Bypassing Backstay Insulator for SSB Radio

[cburger]

I am intersted in adding length to my backstay antena without removing the lower insulator and am wondering if I could just bypass the insulator by attaching a short length of the same diameter wire, 9/32 above and below the insulator with a couple of bulldog clamps?

[Jammer]

You could do that but it shouldn't make any difference in how the antenna works. The electrical length of the backstay, for antenna purposes, begins where the ground wire and antenna wire diverge. Ordinarily that's at the antenna tuner.

[cburger]

Thank you

[Brian.D]

Just so we know, was there a reason to lengthen the antenna? It probably won't net any gain or signal strength.

Maybe instead of playing with your backstay, why not add an alternative backstay antenna. This is a length of wirerope attached to a free halyard and then connected to the antenna tuner. Now you can make it shorter or longer as you wish.

[Jammer]

Originally Posted by Brian.D

Just so we know, was there a reason to lengthen the antenna? It probably won't net any gain or signal strength.

Maybe instead of playing with your backstay, why not add an alternative backstay antenna. This is a length of wirerope attached to a free halyard and then connected to the antenna tuner. Now you can make it shorter or longer as you wish.

The OP's profile shows the boat to be a Westsail 32 which would have a shorter backstay than most boats equipped for HF. I believe there are a couple of lengths that place even harmonics in bad spots, but I can't remember which ones they are. If that is the case, the OP may have to shorten or lengthen the backstay at the top, or do something else like add an inductor or capacity hat, to get it to work on all bands.

[cburger]

Poor reception on 40m, a guess would be current length 23'

[Jammer]

Receive problems on 40m are more likely due to noise or a really bad ground or connection than antenna length.


On HF, electrically short antennas primarily affect transmit because receive is noise limited rather than sensitivity limited.


What you have there should be long enough for 40m once you include the length of the wire from the tuner to the backstay. 80m could be a problem

[cburger]

Originally Posted by Jammer

Receive problems on 40m are more likely due to noise or a really bad ground or connection than antenna length.


On HF, electrically short antennas primarily affect transmit because receive is noise limited rather than sensitivity limited.


What you have there should be long enough for 40m once you include the length of the wire from the tuner to the backstay. 80m could be a problem

There have been contributions from other members indicating that 40' to 45' are about optimum for backstay antennas, would there someting to gain by increasing our length of 23', and would bypassing the lower insulator as indicated work. Ultimately will put an analyzer on in attempt to optimise antenna efficiency.

[j.g.evans]

I have done extensive simulations of my back-stay antenna. I have simulated width and without insulators. The simulations show that radiation couples into the mast, stays and everything else metallic. The radiation patterns are ugly or nice depending on frequency.
I eventually decided to attach the tuner to the back-stay inside the boat out of the weather. I did not use any insulators for I did not want to cut my rod back-stay. The SSB worked fine.

I would be careful attaching to the back-stay wire for fear of causing a point of corrosion. Even stainless to stainless can be a problem.

[waterman46]

Originally Posted by j.g.evans

I have done extensive simulations of my back-stay antenna. I have simulated width and without insulators. The simulations show that radiation couples into the mast, stays and everything else metallic. The radiation patterns are ugly or nice depending on frequency.
I eventually decided to attach the tuner to the back-stay inside the boat out of the weather. I did not use any insulators for I did not want to cut my rod back-stay. The SSB worked fine.

I would be careful attaching to the back-stay wire for fear of causing a point of corrosion. Even stainless to stainless can be a problem.

Yes, attaching wire from tuner to backstay chainplate inside the boat is a good way to lengthen the antenna if OP shorts the insulator as he mentions.

I have not experienced the corrosion issue you mention. How do most folks connect feed lines to SS backstays above the insulators?

[ussvdharma]

Check and see if the wire on the lower portion of the insulator is grounded.....that is important. Depending on how long you want your extra wire, I would to up the mast and add the extra wire from th top of the antenna, OR....Buy a G5RV antenna it installs like an upside down vee and works out fantastic. used one cruising for over 19 years.and with the ocean for a ground...worked the world. G R O U N D...suggest you go to a stained glass store ashore or on the internet...you will find rolls of very thin copper strapping that is adhesive on one side. Run from the grounding point on rear of your sideband down to the inside hull to the tumble-home...part of rounded hull that is below water line, but above bilge water. Run two or three length as far as you can for or aft and connect with soldered strap. You now are capacitvely connected to ocean...consider copper strap (conductor) hull (insulator) ocean (conductor)....a capacitor..you are very well grounded with out actually touching the water....and the ground wire is a heck of a lot easier to hide behind cushions etc when going down from rig to tumble home.

[ussvdharma]

G5RV antenna...run from top of mast down-aft and down fwd...great antenna

[Brian.D]

According to G8JNJ who has done testing with antenna tuners...

"For example, good lengths of wire to use for vertical antennas, permitting operation from 80m to 6m are around 7.2m (23.62 feet (tune for resonance on 10.4MHz)) or 9.2m (34.12 feet (tune for resonance on 8.2MHz)). Note that the shorter length gives better results on the higher frequency bands. This is because the radiated energy tends to tilt up towards the horizon, when the length of the antenna becomes greater than 5/8 wavelength long. This results in poor performance for long distance contacts."
https://g8jnj.webs.com/usingautotuners.htm

Remember these are quarter wave lengths. 234/f(MHz).

Is it possible that you are not getting a good ground? (funny how the word 'ground' is used on a boat in the water.) Just curious as to your setup. Or possibly you might not have good contact some where in the signal path. Tuner issues?

[cburger]

I am looking to optimize for shortwave 20m, 40m and 17m. The boat is currently on the hard for work. Backstay antenna is approximately 23' long.
Running a nice old SEA 222 marine HF radio and an Icom RC-475. Both radios
have a ground wire run to a small Dynaplate. Sea antenna tuner is currently using a KISS as counterpoise, (Plan on changing this).

The marine radio will allow programing of shortwave frequencies and with boat on land have made contacts from NY as far as Thunder Bay Ontario on 20 meters, all the while utilizing dead batteries and the vessels charger providing DC power. The marine radio will receive 20m and 17m very nicely, however 40 meters very garbeled. The Icom using the same antenna and the dual passband feature will allow me to receive 40 meters but requiring a lot of patience and fussing.

If possible would like to optimize the backstay to work with these bands without the aid of antenna tuner and have current equipment work to full potential.

[Brian.D]

Got it. In that case, the best single band antenna would be a vertical dipole. Granted, that is another antenna to add to the boat, but if you really want optimum performance on, say 40 meters, then you really want a dipole. No need for a tuner unless you go out of band for data vs voice vs CW. That might not be the solution you are looking for, but just passing it on.

Bill Trayfors WA6CCA (SK) recommended the vertical dipole and had 2 on his boat. One was for the 20 meter band and the other for the 8 MHz band. He swore by them as being perfect because no additional ground was needed.