6BTV downed in storm. Beware of cheap 'para-cord'.

The 6 band trapped vertical was downed during a series of storms with sustained wind speeds of over 90MPH with gusts over 100MPH being recorded around the UK. 

The antenna was fitted with 6 guy ropes with 3 about 1/3 of the way up and 3 about 2/3 of the way up the antenna the two groups of guy lines were equally spaced around the antenna and secured to large fence posts and one of the small sheds. This appeared to be holding up and working well during the first two storms. Unfortunately as the third storm was reaching its peak at least one of the guy lines snapped initiating a complete structural collapse of the antenna. The bottom section of alloy tubing was badly bent with two of the upper sections and one trap also damaged in the collapse. 

The guy lines used on this antenna were made from the same so called 'para cord', green woven outer covering containing 11 individual strands.  The same cord was also used for stringing up a few wire antennas that survived the storms only to be brought down the following week as we got battered by another storm with high winds and heavy hail. 

Beware of cheap 'para-cord' !  There are many products available that are sold as para cord or shock cord that may be fine for light duty use but simply do not have the tensile strength to be reliable in  harsh weather conditions.  I have repaired the damaged trap and straightened out two of the three bent sections of tubing, The bottom tube section was the most severely bent and will most likely have to be replaced. 

I will be investing in some proper heavy duty, high strength, 'tried and tested' para-cord from a reputable supplier of antenna hardware when the vertical is reapaired and re-erected in springtime.

Like many things, going for the cheap option may do the job under low stress conditions, but will inevitably fail when conditions deteriorate. It is simply not strong enough to handle elevated stress and high peak loading during storm conditions. 

I should have known better but instead of waiting until I could get some good quality high strength cord I used the cheap stuff that I already had in a rush to get the vertical on air. 

Learn from my mistake. Use proper high strength para-cord or proper guy rope from a reputable supplier and avoid the cheaper options found online. 

73 de MM7WAB, Hairy Paul, Ayrshire, S.W.Scotland. 

6BTV up an running.

 6BTV now under test.

After several delays I eventually got everything together and a break in the weather long enough to do something!   There had already been much pondering about shortest feeder run possible while keeping coax out of the way, getting the fatter coaxial into the shack would be a struggle. And of course, where would be the best place to put the six band trapped vertical that could meet this feeder criteria and be realtively easy to add counterpoise/ground radials to as required without causing too much disruption.

It ended up almost in the middle of the back yard, on an existing timber post that was 'over engineered at the time for no aparent reason'  

Fixed the antenna base plate to 4x4in timber post with six 3 in screws. 

Feedpoint about 3ft above ground level, Belden 9913 coaxial from antenna feedpoint to Joint-Box outside shack window. 

 Assembled antenna laid on long bench and roughly adjusted traps with Nano-VNA knowing they all change when up in the air.  This usially gets You somewhere close on a few bands but some will need a bit of a tweak to get them just right for the part of the band You will be working. This may seem like a bit of a pfaff at the time but it is all part of the process to make the antenna work as efficiently as possible on site. After measurments and some testing, adjustments are done one band at a time, working from the highest frequency down until all traps are adjusted and each band is tuned for your specific use. 

When deploying a trapped antenna each section has to be tuned, in sequence, on site for best results so the antenna has to be easy to drop for adjustments. Final tuning can sometimes take many drops and a fair bit of time to accomplish good results. It depends on what radios you are going to run on it and how You prefer to run Your station. 

When using radios tha do not have matching devices, eg; Yaesu FT707s and the like it is best to have the antenna resonant with a good 50 Ohm match for efficient energy transfer. Always best to actually tune the antenna rather than use an ATU to load the antenna system to match the radio.  

Note: Adding ground spike, counterpoise or ground radial wires has significant effects on antenna behaviour, feedpoint impedance and resonance, so make sure all connections are good before final tuning. Adding another 'ground line' means cheeking each band again and adjusting where required. 

In general adding ground radials improves efficiency but they can de-tune the antenna too, so always best to check. 

  In my case two para-cord guy lines get released and two backed off a bit to release all tension that may impede lifting.Antenna is then lifted off base pole and, lowered to ground, tilted down and laid on long bench for adjustments. It took me a few hours to get 10,15,20 and 30m just right before losing daylight and about an hour the following morning to get 40m and 80m a bit better.

I am currently running comaparative tests using FT8 narrow band digital mode on HF bands. 

Switching between 3 antennas, (only two on 80m, 40m)

G7FEK homebrew wire. 80, 40, 30, 20, 17, 15, 12, 10

DX Engineering 6BTV,  80, 40 ,30 ,20 ,15 ,10

A99 (upper element of center fed vertical)  30, 20, 17, 15, 12, 10

When I am not operating the FT8 station, it will be receiving and reporting to pskreporter map.

When left unattended the station is connected to the 6BTV under test.

All grounds and radials will be disconnected during some tests.

Currently running with one 10m ground radial to W.N.W.