Convenience or Compromise antenna for portable HF?!

 It depends on what one considers as good ops!. When speed matters like in regional emergency comms, NVIS strategy is most beneficial. NVIS antennas for any bands are very low to ground often no higher than quarter wavelength. Dipoles or EFHW hung just few feet above ground get this mode going in shortest possible time.

When one is looking for mid to long range distance comms i.e 500Km + and moves beyond those weak signal modes like FT8, JT65 etc., there comes the need of height, optimized antennas or directivity. This article may be of interest to such Ham Radio enthusiasts who are looking into operating beyond regional comms for non Weak Signal modes and do great. This is based on my experiences of last few years on the field portable ops and subsequent 4NEC2 model based verifications.

First thing first - When we look for portable ops such as POTA and field days, one will come across great amount of content on internet webpages and youtube. Most majority suggest use of End Fed Random wire or Halfwave antennas and some use small loaded verticals. But, look, all were looking at activating the park with 10 contacts or having some outdoor fun during the day. Most of the antennas are low to ground or vertical. Especially EFHW is popular because of convenience of multiband operation. Carefully observing the signal reach patterns of their reports, it is relatively rare that they work 6000 Kilo meter+ distances, on consistent basis. One will get to know US operators working other states around or bordering countries. Like wise in EU, they work each other countries and mostly they are withing  couple of thousand KMs. But in VU where is the active ham population to reach? othenr than during regional NET checkin times on 40m? So, mostly one resorts to FT8 or other similar weak signal mode to increase QSO rate (if that is the objective)

I mostly participate in CW or SSB Contests and objective is optimizing DX QSO rates and score with less weight and hassles. I have worked on hill tops, River estuaries, beach areas etc over last few years and evolved my learning with practically building various antennas such as Dipoles, EFHW, Inverted Vee, Verticals (mono band and multi band fan type), VDA (both mono and multi band), Hexbeam and spiderbeam yagis. I would like to keep VDA and Yagis aside this time and focus on portable popular EFHW and verticals.

Following is the Elevation (Blue) and Azimuth pattern for 40m EFHW in inverted Vee configuration 10meter (quarter wavelength) above average ground. Most of the radiation is straight up and at 10deg angle from ground level, it is around -7dB. 

Second plot is for same 40m EFHW at 20m (half wavelength above ground). Now, we can see the elevation pattern is shaping up with -0.13dB gain at 10deg angle. These plots will be same for standard inverted Vee centerfed dipole at fundamental resonant frequency.

But this pattern distorts for higher resonances such as 20m, 15m and 10m bands with additional azimuth wing patterns and lowering elevation angles. Based on the situation they may be taken as advantage or can be disadvantageous.

Advantages of EFHW are many--

a) Requires feedpoint at lower height i.e less coax

b) no more heavy duty pole or support required at center point

c) resonates at multiple harmonic frequencies

If EFHW is similar to dipole, why not just use it all the time?

What the modeling misses is actual transformation loss and RFI. EFHW requires carefully built (often shown as easy to build) 49:1 or 64:1 transformer at feedpoint. And in mono band version of  EFHW, one can construct simple feedline stub to gain the advantage (example JPole) of much lower loss. When operating portable, many compromises made in the name of QRP starting with lossy Coax, fact of RFI pickup is not noticed etc. These can be excuses only for highly tactical and worst case situation, but attentive ham should be careful more than QRO ops as inefficiencies adds up. For example: Let us consider 10W output from Transceiver connected to EFHW with RG58 of 10m length. Let us assume with 1.2:1 SWR antenna. This delivers approximately 9Watts to feed point. A transformer loss of 20% on this 9Watts brings down another 1.8Watts i.e power delivered to antenna will now be 7.2Watts. So, even before one says antenna is efficient or no, we have 28% reduced power already delivered due to convenience we wanted. OK, now most of the time I have been told these losses are negligible and no one will differentiate on the other side etc. I agree to some extent, but on the edge condition, these negligence matter a lot and which could be fixed easily.

Adding a coax such as RG213 or LMR 400 and feeding antenna directly such as dipole ( or vertical) without transformer is next step up bringing the losses to less than 10% (efficiency goal in my case). I made first SSB, CW DX QSOs with simple fan inverted Vee only. High apex works always! Verticals are though directly fed, will pose roadblocks in to efficiency journey if not given attention to its ground system. 

I have both QRP and QRO dual core EFHW transformers in my portable kit as fallback. But do I prefer them over dipole?. No. because there is one more reason I have not mentioned earlier with importance, i.e RFI in the Coax line leading up to shack. Unbalance nature of the random wire and EFHW, forces RF on outer shield of coax in both transmit and receive. While transmit RFI is obviously experienced in causing interference to other nearby transceivers, interconnect wires, and if QRO, tingling sensation while speaking to handmic/keying and distorted audio etc. Receive issue is even worst as it picks up local electrical noises and raises the noise floor. To minise RFI we can add counterpoise wires or choke on the line after few meters from transformer etc. But the point is convenience comes at price.

So what other options?. Ofcourse, there is dipole when 1/2 wave height could be established or verticals good radial system. Following are two plots, one on the left is ideal vertical(needs atleast 16 radials or more) on average ground and on the right side with single tuned elevated radial. While two or more elevated radials provide balanced omni pattern, single radial provides some directivity in the direction of the radial. This type of system was practically tested at one of our early field experiments for 80m band which can be found at Blog post link

Here is overlap of two elevation patterns. My experiences showed that when no other antennas are close proximity, having elevated tuned verticals are advantages as it becomes easy for field portable to achieve better efficiency than few ground level radials.

Also, if we are at coast verticals even work much better at 5 to 15 degree elevation angles for great DX. But dot not get overwelmed with EFHW stung vertically to think it will perform same for all the harmonic bands. Just like EFHW in inverted Vee or horizontal position, distorting patterns on harmonic frequencies, vertical also forms higher angle signals which will not be useful in long range.

So while we chose the antenna at hand as better than none, when there is choice, make optimal use of them for the situation, location and purpose we intend to. Afterall, Ham radio is a learning and advancement hobby, just try these and prove!

Have fun

Kiran VU2XE

W6PQL Amplifier's intermittent RX issue troubleshooting and sequencer adjustment

 W6PQL amplifier is great modular amplifier design. Since I had homebrew assembled in 2015/16, it has proven very solid and reliable. I have some issues with Directional coupler and detection of signals to represent reverse power accurately as per Jim's design. However, other than this aspect, i have used the amp in many contests and activations. Last year(2022) during CQWW CW contest, I realized that sequencer is slightly slow in switching back to RX from TX mode. Some of the stations I did not copy either first character or sometimes missing dit or dashes of the first character. This was not serious issue, but anyways, once you know what adjustments to do internally, you tend to tweak it towards perfection. I tweaked the timing so that its faster switching in sequence. 

During the CQWPX SSB contest i did not realize any issues. And after all SSB signals are delay start by human nature of speaking into mic. Also, problem of hot switching might have started during the WPX SSB itself , but did not come to surface. During WPX CW, My entry was bit delayed due to exhausting MQTH work till previous day late night and tr avel related fatigue.  VU2VTI was the early starter at VU2REC club station for the contest. When I started on the bands, at first it seemed all ok. But, suddenly started feeling the RX is weak sometimes and delayed to full signals. I thought it was due to some ionospheric disturbance. But when it continued for some hours, i sensed it unusual. Asked VU2VTI to be on my system and run the contest for few minutes. He confirmed that it is unusual and something might be wrong with my Amp or Radio. I then disconnected amp from the path and observed no issues with RX drop. This confirmed me that Relays inside the Amplifier might be damaged. No time to fix and no spare relays on hand. I packed my amp to carry back and continued the contest with TS590 barefoot.

Back at home, after opening the amplifier lids, first thing visually checking the three LEDs in sequence i.e. Hold off ALC line, Trigger Relay line, Release ALC line. Initially it was almost instant, I adjusted PCB variable pot to have some visible lag between the events. There was no RF input given to the amplifier, all testing was done using a SPST switch to PTT in RCA plug. This allowed me to rapidly check the working. Next came checking the Input and Output  Relays. While input relays typically take less than 10Watts or less in the path (my drive power), output relays handle upwards of 350W or more.

I had a hunch that output relays might be the issue due this factor. While switching PTT line, keeping my fingers on the relay, I sensed no movement in the output relay. Thanks to modular design of the amp,  i could desolder the output relay PCB and test it separately. Found that relay coil was showing higher resistance and was not energizing. This is Omron G2RL-1E relay and fortunately, i had few of them in my spares. I did replace the relay and test OK.

This incident has taught me something very important about sequencer lines and never to be too greedy beyond the design specs. By properly adjusting PTT delay for Amp (i.e RF hold back after PTT switching), we can safely control the TRX path for signals. Typically 100ms is what W6PQL suggests (Hold ALC line + 50ms delay+ trigger relays+50ms delay + release ALC line). 

Now will have to wait for next contest or event for my setup testing in real situation.

Hope this helps someone in similar situation.

VU2XE

CQWW CW 2022 VU2XE SOAB LP - Confusingly amazing!

All my limited understanding of HF propagation went on toss :). how much should be SFI for great openings on 10m?.  SFI was 109 over the weekend and N0NBH solar widget showing 10m band as poor with A =10 K=4 etc and I did over 600 Qs just on 10m for the weekend!. I am really confused but even more amazed with what we didn't know happened at bottom of HF comms pyramid!. Is that Nature's miracle to keep Man amused and grounded. 

Background:

Last 10 years in contests, I have not experienced a condition where Qs poured this heavy. Really.. there was no time to pee, even gulping water seemed difficult in midst of that high rate hours HI HI! and this is story for me of  more philosophical revelation and may be a start of new era in Radio contesting years. A story of learning, struggling over years for location, evolution in antenna designs to suit locations, right frame of mind and finally saying - "this is all I had, now what?". - take it easy !

Last month, myself and VU3SPD - OM Vatsa did low power Multi Two SSB contest from this hotel in the northern outskirts of Bangalore. Location was quiet, radio friendly. Though it was not at high elevation, HFTA showed good signal probability at hotel's 30 to 45feet high terrace. I was suffering from heavy cold and throat infection for the voice contest. Some heavy tripping of W6PQL amp due to SWR issue lead to HP Blade ESP120 DC power supply problems. We made decent scoring of ~650 Qs. For last few years, I have traveled 350km to beach location near my native for CQWW, but this time due to MQTH, decided to operate from this known location nearby.

My amp was not giving out more than 150W with another standby power supply due to efficiency. W6PQL suggested to reduce amp VDD to 40V which can increase BLF188XR LDMOS output to 400W (for better efficiency at lower input power). I could not adjust the power supply below 46.5V due to limitations in that SMPS design. So amp was kept aside for CW contest. I started preparing my mind saying my highest till date was in 2015 that too with 50W power and now this 100W from rig is 3dB higher. So scoring goal can also be higher than that of 2015 to start with.

This also allowed me to relax, as when I travel with high power gear there is always some anxiety around local electric power issues, extra weight, SWR etc. I had done a presentation during Hamfest India 2022 where I mentioned about "Pyramid of HF Comms" with 5 layers. At the bottom is Ionosphere. My point was - to make comms successful, Operator at top is at the mercy of Ionosphere at the bottom and all other layers are instruments in between. With our limited understanding of Nature, we have to be in submission mode to be humble and accept what comes. - a hard learning over years. So we have to put efforts, learn and advance, but always have to be cognizant of the fact that we are tiny particles in larger context of Nature and what we don't understand (call it miracles?)  

(Disclaimer - many videos, images, background music used for this educational presentation are from youtube, pixabay and other channels. All credits to them only. Thank you in advance for your shares)

Setup

This contest seemed like summary of what I presented in text book style. My plan was to keep it simple, using homebrewed triband hexbeam with fishing pole and dipole for 40m. 

Soon after hotel checking-in on Friday @7AM, I got to their terrace to unpack all antenna wires and coaxes. First was to set hexbeam. Clock work starts with my lightweight mast and center post assembly. 

Many aspects of this were designed only for temporary setup and knowing that we have to be ready for any issues. One hour was my target and I did manage to complete assembly within that time. But tuning took another hour for SWR match.

During assembly one of the spreader leg got fractured and it was repaired on the spot with a small PVC pipe section lying around. 

Yeah. Finally it is all done with one antenna by 9:30 AM. Does not look perfect arc, but it seems performing. All parts used in the project were locally sourced (Decathlon for 5m fishing pole, hardware shop for PVC pipe, 1 sqmm wires, vinyl base plate, L angles, worm clips etc.)

Now for 40m antenna-

Few days before the contest, I had modeled 40m dipole (4nec2) with one leg bent towards floor at 45deg, other in horizontal and checked adding a driver element. It all showed good 2.5 to 3 dB better gain and FB of more than 20dB. So why not carry wires?

There were two levels on terrace. One ~30ft high was adjacent to room and another above the room at 40ft. There were few wall clamps permanently fixed on the south sides which were used last time for spider pole support. This time, it was easy decision to use the same. Used 9 sections of 12mtr spider pole, attached choke at 7mtr point and dropped a thread from 9mtr point for holding director element. First tuned driver element to 6.88Mhz with director decoupled (dropped to ground). Then raised director at 15 feet horizontal distance  from driver (distance plays role in FB and SWR which was adjusted to get best). All this took couple of hrs. 

By lunch time, I was done with all terrace antenna work. My friend VU2CDP was also at an excellent field location near Pune for the contest. He kept chatting with me on his progress and challenges there. 

Afternoon, I went on to setup working station. I also tried amp for power output with standby DC supply and decided that additional 50W is not worth keeping extra hardware on the table and dropped to barefoot 100W with my TS590.

Some more fine tuning of antennas for SWR and test of FB was done in the evening.

Desk looked neat and promising for upcoming contest day.

Contest-

As in my 2015/16 contest, first few hours seemed to determine the outcome and it did so here as well. First session on Saturday morning till breakfast at 2:30 Zulu ended with 59 Qs on 40m. This gave me confidence that I may be able to beat my previous low power scoring. Then started on 10m with Japan. What a discipline in pileups as well!. It was like some traffic cop sending them one after other. Continuous Qs till 3:30Z. Switched to 15m at 3:30Z with JA pileup till EU started popping/taking over around 4:30Z. Pileups on both 10m and 15m alternating when one slows down. Continued till 12:30Z on these and then switched to 20m. 20m was comparatively slow paced till 16:30Z with many NA popping in between. Whole night was spent on 40m with a 4hr sleep breaks. Later VU2CDP informed me that it was prime time for 40mtr. But I could not keep myself straight for both nights during that time. First day closed with 1K Qs in total. 

Sunday started with good Caribbean multipliers on 40m such as V26K, PJ4K, ZF1A, PJ2T. Then kept runs toggled between 10m and 15m as per run rates. Maximum I could handle was 120 Q/hr on 26th. In between I thought "oh lord, I asked for good conditions and you are just pouring". Day2 also followed the same pattern of follow the Sun i.e. 40m till 2:30-3Z. 15/10 for JA till 5Z and then continue with EU on these bands till 12Z. Around 12Z, started checking 20m. Interestingly on day 1, 20m was not having big signals till late evening local (i.e 12:30Z). My reversebeacon.net spots showed good signs on all bands. With low noise floor, Except  sometime after evening greyline, I could copy much weak signals. Some of those signals didn't even move the S meter needles on TS590. I closed my contest with excellent team at A44A on 40m at 23:57 completing my all band contact with them.

In no time, I was packing and by 2Z  was on road back to my home reaching safely back and logging to MQTH remotely!

What are the learnings this time?

What worked very well-

Multiple field ops in last couple of years, helped to refine the go kit for contests

1. Filter sets, Amp, Radio, Ant, Tools all in their respective bags
2. Antennas are mostly for the location & situation with some enhancements
3. Most of the clamps do not require any tool, use plastic butterfly handles for quick fixes. 
4. Minimal waste of plastic and ties -replacing with rubber tie wraps (inspired by bongo ties). 
5. Understanding of antenna models and tuning procedures for multi element yagis really helps in adapting to location
6. HFTA is a boon before reaching the location, do physical recce for noise floor and friendliness
7. Keeping the relaxed mind all the time and sharing fun bits with buddies during ops really boosts morale
8. Packing from one contest is preparing for the next one. Keep the kits in shape after each contest  - check wires/coax for damage, clean connectors, keep tab on spares (nuts, bolts, solder, guy ropes etc) 
9. Carry extra chokes with SO239s. it helped me to resolve RFI issue of USB audio connection drops for QSOrder

Out of all 5 layers of pyramid what matters most ?- 

While multiple ops optimized instruments over time to some extent (rig, antenna and location choice), Top of pyramid - The Operator (who seems to be understood and under control ?) needs more refinement and higher level of respects to The bottom of pyramid - Ionosphere (The most illusive and not in control !) 

Operator - Need to work on optimized schedule for night time shift, multiplier hunting, be smart to apply ideas for the situation

Ionosphere- We can only have general trends of signal path. But what will happen on contest day, no one can predict. Impossible happens within minutes. We are just witness of  fine balance between Sun and Earth spheres

Operator is at the top of pyramid but he is really at mercy of bottom of the pyramid - The Ionosphere. But when all things go right CQWW CW 2022 happened to VU2XE setting higher bar for next time!

What about you? Did you experience the magic? Hope you enjoyed the thrill as well..

DE VU2XE Kiran

CQ WPX CW 2022 - VU2XE - A Plateau of constraints vs contentedness

Many times in the past I had participated in some contest without understanding terrain, antennas, propagation or operating skills. But I always had aspiration to learn by being there. Over the years, I have tried to learn and hone skills of Radio operating in crowded conditions. I have taken lot of frustrations in having high expectations and not performing to the mark. I have learnt (sought of) how to set my own goals per my understanding of conditions/constraints within which I operate. 

When one develops scientific understanding behind how and why things really behave the way they are, the pleasure it gives to the each QSO one make multiplies. I keep that as my personal scoring criteria above all contest multipliers. For me, not black box dummy contest parrot that gives kick, but understanding the rush of electrons, EM acceleration via antennas, medium through which waves glide across the globe and finally being heard at other end that brings excitement.

Some contests I prepare for year long and long for it. Some like this CQ WPX were cause of a sudden opportunity I encounter in between my personal appointments at my native location.

Just a day before while a call to attend a personal appointment was scheduled, I realized it as WPX contest day as well. So why not carry my rig, coax and wire antenna?. 

I knew I would not participate fully, but Sun's growing glow could not resist me. I decided to operate only 15m as it suited space and time constraints. Quickly prepared dipole wires and packing essentials along with my TS 590. I also took my 12 mtr spider pole for support. My native place property is surrounded by 15 feet high tile roofed houses and any antenna had to clear those roofs. For 15 meter band dipole, 1/2 wavelength height is around 25 feet , which is just above the surrounding roofs. But I had 25 feet blockage on east to South west direction due to sloping hill and crowded houses there. 

The only variable I could adjust was my goal of QSOs :). I brought down the goal to be 100 QSOs and be happy anything above it.

All things set, I now reached location by overnight bus at around 1 UTC, had an hour to arrange wires and look for 15-20 feet bamboo. After refreshing, completed my main appointment in the morning and returned home by 5:30 UTC. I had to now raise  dipole and connect the radio. All worked fine and by 6:30 UTC I had first QSO with OK1 station.

It was slow S&P contacts through out with sometimes running to find any possible onlookers. Reverse beacon confirmed my understanding about high angle signals from the low height. Normally the way I check it is, seeing how far my signals are heard when band seems to be just opening. Initially my signals were only heard in YB, 9M (AS) and ET3, 3B8 (AF), then slowly my signals were heard in East EU and then to West EU . While some other stations(with lower elevation angles) from VU were heard in EU much earlier in time. Nothing of concern as I know my constraints and aware that those signals will appear soon with my butt in the chair :) And they did arrive to fill the log. I wound up Day 1 with just over 100Qs at around 15:30 UTC.

Second day was again having some other personal work taking priority, spent only few hours at radio. and by 10:08 UTC I had to close ops with total of 145 QSOs on 15m and 19 QSOs on 10m. No NA/SA stations worked this time as I closed my operating early on both days.

Some hams think contesting is waste or rubbish on air etc. For me it is an opportunity to uncover the next learning potential in true Amateur Spirit. I try to introspect what went well/wrong and why. What I could have done better with limited resources. How the experience of next one can be made better. How my experience can help many more like me etc.

When one struggles with constraints, learns and figures how to be content - "Nirvana" is achieved. True for me, what about you?! 

73s

VU2XE

Protect connectors with this simple Hack!

 Amateur operators use many type of connectors in the shack and in the field. One of the most common connector I use is UHF. When they are used in outdoor transmission lines, we normally waterproof them using rubber tapes, insulation tapes etc. While they are not in use, if they are left outside in garage or workshop, dust/moisture ingress will deteriorate their performance over time. Often, we should use contact cleaners before taking them out for use.

In the past, I have used plastic caps (MX in India sometime comes with such caps) and metal threaded dust caps as well. But, they are hard to find in India. I wanted a easy solution for making quick n reusable protection for many UHF connectors I had in my box. This is a problem while carrying devices to portable locations as well, especially unprotected PL259 connectors take hit when uncoiling coaxes. 

Here is what I came up with available heat shrink sleeves. Yes they are not good as threaded caps, but 

1) Keeps connectors from sand, dust, water ingress

2) Reduces wastage of insulation tape during transport or uncoiling coax

3) Can be quickly made in the field too!

73s 

VU2XE

CQWW CW 2021 - Multi Two VU2XE and VU2CDP

Note: 3830scores.com has operating notes on this contest:  https://www.3830scores.com/showrumor.php?arg=lRabzesimgvgD

Just after my CQWW SSB attempts at Mulki in South Karnataka coast,, VU2CDP got in touch with me for a much serious multi efforts. I agreed on a low key efforts. We had limited automation resources and hence settled on multi two format just to have both of us operating. Having decided about participating in the contest, next came from where? and obvious choices would be close to Sea having good property space to put antennas. Last few years, I had been scouting for quiet radio places to operate contests as I was restricted at home QTH. One place out of my scouting experiences comes to my mind each time was near Coastal town of Udupi (my first experience at this place with VU3NXI in 2017 posted at http://kiranpadiyar.blogspot.com/2017/12/lowband-hf-experiments-near-coastal.html). We shortlisted that river estuary point homestay(AirBnB) near Udupi with many coconut trees and comfortable self service. It was convenient for me to travel from Bangalore and for  Deepak to travel via overnight train from Mumbai as well. Also, I had kept most of my equipment at my native place which is 80Km southwest of this place. So logistically it was convenient.

South West

Next was antennas, Deepak suggested to have mono banders to reduce interactions. Though my Triband VDA antenna with Triplexer ( homebrewed VA6AM design) and High Power BPF(homebrewed PI4CC design) set I had would have sufficed, There was some tuning difficulty observed last time and I thought it is better to avoid any component failure probabilities or delays due to unconventional antenna designs. So, I got to design  monoband VDA using 4nec2 software with locally available 1Sqmm PVC housing wires. Based on earlier experiences with VDA, I made center cross joint with plastic cutting boards, Coax connectors to go with PVC end caps etc. All three VDAs were designed and wires were cut/prepared for assembly. For RFI choking, we used coax clamp ferrites. For 40m, I had half square array and Spitfire prepared on earlier trips. For 80m, I prepared vertical with two elevated radials.

North West view

Our Homestay was only available from Friday and we wanted two days prior to the contest. Owner obliged by letting us to use the property for putting antennas on Thursday and later they allowed to check-in on the same day as no other guests were present. We found that, two days are very minimum for setting up such station. 

I had reached Udupi on Wednesday for arranging all antenna stuff and doing prelim work like PVC cross arm assembly, cleaning up Coax connectors etc. On Thursday morning, VU2CDP arrived from Mumbai train and after a short rest/breakfast, we proceeded to homestay site. We carried only antennas, ropes and coaxes. Owner had arranged for Coconut tree climber for our antenna hoisting. We quickly got into action with location for VDAs, vertical and dipoles. 

Kiran at far end maneuvering rope for 40m dipole

We chose tallest tree ~60 feet for 80m vertical (it was faithful one which supported our fan vertical for 40,80 and 160 on last operation here), a ~50 feet one for 40m and one more as standby. Within a hour all pulleys with ropes were tied to the trees. We then got in assembling VDA antennas 20m first and then 10m and finally 15m. 20m tuned on dot on first attempt, but later we moved the antenna farther to avoid tree leaves touching the elements and changing SWR.

VU2SBJ Sri, VU2CDP Deepak, VU3DMP Chetan
and VU2XE Kiran at Manipal

VU2CDP with VU2BQN Dr.Manu and VU2NJN Dr Soma of MIT

By afternoon we were done with 20m VDA and 80m vertical. We found that we need more coax and requested our friends VU2SBJ, VU2BQN for help. They arranged for additional Coaxes. By evening time we were ready with 40m Vee dipole (I prepared this dipole with wires of halfsquare ) at around 50feet apex and ~25feet high leg ends. Next day we completed 10m, 15 m VDAs and final station layout setup as well. During the final testing, we had VSWR swinging with 20m VDA. That evening VU2SBJ, VU2BQN and VU2NJN visited us. We figured out a faulty barrel joint and fortunately VU2SBJ had one extra barrel which sorted the issue.

VDA Coax feeder arrangement with PVC cap

Then we were left with N1MM network, where we struggled a bit as interlink was not happening. I called VU3NXI for help and bit later figured out that netbios name had to be placed in Network status-> Edit Computer Address section of N1MM software. This was not necessary in last month's contest as it was detecting other computer automatically. So all sorted, we took a breath. 

Now, It was all upto Sun god to grace some flux on earth and of course He turned his major Spot region and flares this side for increasing SFI over 100 on time for contest!

N6RK Loop for 80m

20m VDA Tuned at once!

 

VU2XE and VU3DMP Fixing 15m VDA

All certain done, we were ready for the contest on time. We decided that we both will run at around 200W only to avoid voltage drops. Both of us got to bed by 11PM (contest starts 05:30 AM local for us). I am unsure whether we got good sleep or no, as the restlessness to get on radio had caught us hard.

Contest morning - started very slow for us, But we noticed that both of us could not run with amplifier even at 200W. So one had to be barefoot. On first day, I went barefoot and Deepak was on his K3+KPA amp - running. This was major setback, because we found 15 and 10 opening at same time in the afternoons. We could see around 1200 Qs by that night. I took early time off at night at about 10:30 PM and Deepak kept on Radio till late morning. 

Next morning, I got chance to run with 400W on my W6PQL amp, I continued most of the time running 15m. 10m was again very good that day and Deepak could not use amp due to voltage tripping issues again. We might have lost working few hundred Qs due to this power issues. We had tunnel opening to NA on second day which gave us a bump multipliers. PY, LU stations were having multiple clear opening to VU and helped us in boosting scores when QSO rates from EU were low. We did not find much JAs in our pipleups this time even during our morning 15m lookouts.

Our VDAs worked exceptionally good as they were only few feet within saline water. Its directive gain and F/B ratios were just amazing. On low bands of 40 and 80 we could hear signals even if someone whispers hi hi!. Overall we made 2735Qs which is very close to our set goal of 3K QSOs, and very satisfied with operations. 

End of contest celebrated with glass of buttermilk!

Few takeaways:

1. We noted that we could have used automated switching to jump on other bands quickly to reduce time lost etc. This contest had many coax changes and mistakes during such change over. Probably its time to put my High isolation A/B switch matrix to use in next one.

2. Simple dipole on 40 and vertical on 80 were good enough choices. Probably next time we will look into some additional directional gain to these

3. Power Generator is must at such portable location for bigger scores. Though we could run on barefoot and one amp, we could not benefit from simultaneous band openings. W6PQL amp uses HP blade ESP120 supply which has broader voltage range than KPA500 which seemed to trip with voltage drops.

4. We need to figure to connect local router with some internet connected Wi-Fi device for cluster spot feeds and real-time score reporting. This time we had to connect our laptops to phone to refresh scores etc. and then connect back to local router. bit cumbersome.

5. Overall getting better with portable contesting going on air time by travelling lite, simple layouts, efficient station etc.

Our equipment this time:

• K3 with KPA
• TS 590  with W6PQL Homebrew amp
• VA6AM Homebrew Low Power Filters for 20-10, W3NQN filters for 80 and 40m
• VDAs for  10,15,20m
• Inverted Vee Dipole for 40m 
• Vertical with two elevated radials for 80m, N6RK Loop for Rx

Our quest to improve operating continues. Hope to see you in the next one!

DE VU2XE

Triband VDA antenna update (V2)

 Last year during CQWW SSB (Oct 2020), I had tried to tune my own designed triband VDA antenna. Whatever I tried, it seemed that antenna was not tuning or getting out well. Youtube video on that effort is at https://youtu.be/tJb-NoXO6V0

Couple of months ago, I was pondering about the issue with VDA and realized that my design was not considering PVC jacket dielectric loading (velocity factor). That  made me to load the model(4NEC2) with PVC jacket and check once again with same dimension. Oh. My.. Yes, I was way too off from the design frequency and no matter what I did on ground, it would not have given right results. 

So, a month back during Covid19 native place stay, I carried the VDA to be installed at my garden and check with PVC adjusted dimensions. And I was finding the spot on tuning. I know, triband on a single pole is compromise due to spacing requirements and height above the ground etc. But this is something I could live when Sea is washing its base, when I travel solo etc.

With this test done at home, I got opportunity to test it right on the beach when I was invited me to operate at Kapu Lighthouse AT8KLH near my hometown. It is a week long activation of lighthouse with many events and teams planning to operate from the location. I did quick recce of the place on my way to Udupi where I had kept most of the cables and poles from last WPX contest. Found very friendly neighborhood and a school on the beach next to lighthouse - very ideal for the operating. There is greater collective story to be compiled once the activation is complete. I am sharing my short 2 day participation experience with VDA.

Putting any antenna on beach during monsoon season is bit of pain, we took 2-3 hours to just put the antenna and secure with guy due to heavy rains. Once it was erected with help of Lakshminidhi VU2WFN, SWR plots were checked to be on CW portion of the band where myself and VU2VTI Murthy wanted to operate. Though I had carried some heavy filters etc. to operate multi, we could not due to lack of electric power at the premise.

Anyone who has operated the VDA from right on the water edge know how signals come. I can make a quick contrast with eating food right out of frying pan (still sizzling) vs somewhat cold but still fresh on the table Hi Hi!. Signals with incredibly low noise and crisp right out of the operator's shack on the other side of the globe. We made a 650+ QSOs with many breaks and change of operators etc. till we closed later evening on 15th. Epitome of thrill when one could be in the center of massive pileup and in control of it!.

Following is the 4nec2(freeware) design file if someone is interested in replicating/improvising.

https://drive.google.com/file/d/155F-yHVCxiO9XVuinu8rqDsIFrOxilXo/view?usp=sharing

There is lot of opportunity to optimize further especially for F/B ratio. Here are some plots from 4NEC2

Note: This VDA requires 10mtr tall support (I used 12mtr spider pole with last two segments collapsed). At the Cross section, I used a cutting board material with drilled holes for wire ties. For cross arms (total length of 2 meter), I could have used PVC pipes, but I had couple of Caperlan fishing rods (1 meter collapsed length). This antenna did not hear anything from back. Just to note, there was a small ridge (15ft tall) at the back side towards south east/east. which might have helped in reducing noise/signals from back. Following reverse beacon report and QSO stats shall summarize the efforts well.