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.

Update on portable HF vertical antenna (40-10m)

Couple of days ago I had posted a writeup on my trial AHVD antenna. While it seems very clean design, to get efficiency out of such asymmetric dipole requires careful adjustment of vertical element vs radials (asymmetric ratio). Elevated legs gives it further boost due to decoupling effects from lossy ground. It would have been nice to have properly marked telescopic Aluminum tubing to go for short trips. However, unavailability of such fine tubes here, drove me to assemble wires and mash them with Aluminum L angles, center boards, wires, nuts n bolts etc. I thought this is bit too much for my operations. What else I can do if have to cut down on poles required, remain stealthy and light weight?. 

Circling back to the basics, Why not ground mounted vertical with few(8 to 12) short ground radials?. I may lose bit of efficiency, but hey, anyways, I am not going to place this antenna on a poor ground for serious contests or DX operation. So, quickly turned the AHVD to simple vertical system with same Prolite tripod stand and single 5m Caperlan fishing rod.  Tripod was just at 4ft level where the central connector went in. I placed air core coil which was designed for 40m AHVD through the base of Caperlan rod. I removed base plastic cap of fishing rod and pushed it over the top of Tripod mast (with some rubber pad inside for cushioning) for around 6-8inches. I used around 4.5meters of wire to go vertical and 6 random length (4 to 5 meter long) of wires on the ground. Beauty of the system is that, I can quickly adjust the length of vertical wire which is held together to rod by few velcro straps and insulation tape. Also, Coil is not used for any bands above 20m. Anytime, I can convert it to elevated radial resonant system with right lengths as well. 

When I first checked SWR with my analyzer, wire was fully extended to the top of rod and resonance was at around 6.9Mhz with coil in circuit. I then reduced wire length ~0.5 meter lower and adjusted the coil winding to get resonance at around 7.1 Mhz 1.05:1 ish and almost flat from 7.01 to 7.2Mhz. 

Then I bypassed the coil to check the 14Mhz band which was found to be below 1.5:1. I could have tuned 14Mhz first then used coil to tune 7Mhz band, but for now, its good for me!. 

Happy with this experiment. I will be trying it at few places in near future.

Here is a short video of this setup and few photos.

27 turn loading coil is wound on a 2inch PVC pipe former with 1.6mm enameled copper wire. 

When the Coil is  removed from the PVC pipe, it slightly expands to ~55mm diameter. I then used few pieces of blank PCB material(without copper traces) and glued it at two places to hold the shape. 

Youtube link is as follows: https://youtu.be/T8sd8qcXF_M

What is the difference between AHVD and vertical? : 

AHVD is as name suggests, asymmetric vertical hatted dipole. In this system, one leg is longer than others normally by a factor of 1.5:1 ratio. i.e. vertical leg of the dipole is approximately 1.5 times lengthier than horizontal legs. Horizontal leg is for capacitive loading and hence the name "hatted" (hat is at the bottom instead of at the top here).

Vertical has two popular varieties, with elevated or ground mounted radials. AHVD may seem similar to elevated vertical, however, traditional elevated radial system is of almost similar length as of vertical radiator. I have not done any study of practical signal strength difference between two, as I did not had both of these at the same time. However, I feel both above have their merits and draw back being sometimes one may feel elevated legs/radials are obstructing and they require tuning carefully to a band.

Ground mounted  vertical requires many radials as possible, and efficiency depends on soil condition a lot more than elevated one. However, because the radials need not be of quarter wave, it has advantage of carrying bunch of wires and laying on ground.

 

Trial with portable Vertical antenna (AHVD) system and Fiberglass material for dielectric support

Disclaimer: I am no expert in the field of dielectric effects on Electro Magnetic Waves and antennas. This article is just based on my experimentation to find suitability of antennas/support for my QTH requirements. Also, no commercial interest is claimed for the source materials/brands mentioned in this post.

Recently due to Covid19, working from remote has provided some advantages to me in having some quality time with family and also to spend some time in the radio hobby. In last few years, I had diminishing interest in radio from my home QTH at Bangalore due to nearby obstructing buildings and also due to heavy morning QTH conditions. However, I tried to keep some interest alive in radio during contest seasons by mostly travelling to my native QTH near Mangalore and setting up some station there. 

Many new challenges there prompts me to try new ways to get signal out whatever little extent it may be. Thinking portable is a new mantra I am adapting to have some pleasure operating from places I go. One key challenge always is easy to carry and setup antenna system. Ofcourse, if NVIS communication is the purpose, simple low dipole/inverted Vee would be the best bet. However, for DX, it is low angle of radiation which is of particular interest to me. Only two ways to get such low angle radiation, one by having high dipole/yagi of some sought or secondly by deploying an efficient vertical antenna. During CQWW SSB Contest 2020, I had tried my hands at 4NEC2 antenna design software and deployed antennas at beach location with little success due to practicality of nice looking designs!. Making deployment simpler and repeatable was key to success. This year during 2021 CQWPX CW contest, I learnt that even simple vertical system can get me a bunch of QSO count required. However, it was not efficient and repeatable due to ground/elevated radial support system. 

Checking internet, I came across designs of Asymmetric Hatted Vertical Dipole(AHVD) from KX4O (hamradio.me) and also commercial bravo antennas from N6BT etc. Designs looked very similar to elevated radial verticals we tried earlier, but with better supports and asymmetric loading technique. Due to lack of telescopic tubing availability, I tried to make prototype vertical using prolite tripod, kitchen cutting board, aluminum 3/4inch angles, caperlan fishing rod and bare copper wires. Just by adjusting lengths of wires as per KX4O design  one could easily change bands. I made another small improvement to move down to 40mtr with ~12uH coil (adjusted by trial/error) on 20mtr dimensions as well. Though I could not make much contacts due to placement of the prototype antenna, I got some 20mtr CW DX contacts.

This is a great systems to try during field days and other portable ops for sure. Attached are few snapshots and a short video on the same. 

Antenna at ~4ft level            Loading coil between left leg and top vertical. ground only connected to                                                  right leg. Adjust the inductance ~12uH 

I tried this antenna only for 20mtr with 6.07mtr vertical wire and 3.96mtr each horizontal wire (adjusted a bit to get lower SWR). 

Following are few snapshot of my LCR meter showing reactance change with few common materials we use a support mast/junctions etc. I measured these inductive reactance changes for 1/2 inch dia loop with 4 windings.

              AirCore                               Aluminum tube                                 Caperlan 5mtr pole

Calcutta House Fiberglass tube        Kitchen plastic cutting board    12m Fiberglass Spider pole

I felt, Caperlan pole is very close to spider pole in dielectric characteristics. Though it is very thin at the ends, bare copper wire of 1mm dia will stand straight without any issues for portable setup. For horizontal legs, I used 3mtr poles. I tested effect of Aluminum just as a conductive material reference.

My inductance measuring loop over the fiberglass material.

A short youtube video of this setup is available at https://youtu.be/0F2CoAb8DQM 

Cheers

DE Kiran VU2XE