Tactical All Band End Fed HF Antenna

Started by Lamewolf, September 08, 2016, 10:58:04 AM

Previous topic - Next topic

Lamewolf

http://vk6ysf.com/hf_tactical_%20antenna.htm

Anyone tried or experimented with the type of antenna above ?  Thinking of trying to build one just for kicks.

gil

#1
I wouldn't really call it an end-fed.. You probably would need a tuner anyway. No antenna showing a low swr on all bands is going to be as efficient as a resonant half wave..

Gil

Lamewolf

I guess you are right about it not being an end fed, but it is supposed to be less than 2:1 swr from 2 to 30 mhz.  And yes, its probably not very efficient but would be quick to deploy. I have a 9:1 unun I built and I have the wire and the resistor and plenty of metal tent stakes to use as the ground spike, now all I need is to find the time to put it all together and try it out.

gil

Please post the results of your experiments if you do.. It would be interesting..

Gil

Lamewolf

Well I have already built something similar and that's why I already have the 9:1 unun that I built.  The other antenna was a vertical half rombic that had the 9:1 at one end and a 450 ohm terminating resistor at the other end - <2:1 swr from 160 to 10 meters  from a 100' wire.  It is deployed as an inverted V with the center supported at 30' and the ends close to ground and connected to ground - worked much better than I thought it would even with a measely 5 watts from my Yaesu FT-817 !

cockpitbob

Any antenna with a resistor in it makes me suspicious ??? .  The only thing a resistor can do is burn power. The resistor in the kit you bought doesn't look very big, so if it will do 150W as described in the article the resistor losses can't be much (otherwise the resistor would smoke). 

If you have a 100W rig and want to test the resistor's losses, I have a trick for measuring losses in traps and such.  Stick a chunk of candle wax on it, hoist up the antenna and broadcast a 100W carrier for a few seconds.  When you lower the antenna, if the piece of wax looks like it melted it got to at lease 160F.  Of course the distribution of current and voltage along the length of the antenna will be different on different bands so you'll have to try it on every band to make sure one band isn't going to smoke the resistor.

But remember, even if 75% of that 100W goes into the resistor, you are only down one S-unit at the receiving station (4:1 difference).  So if the resistor does get a little warm, I wouldn't worry too much about it.

gil

Good point Bob. I think many compromise antennas radiate only a fraction of applied power. Many HAMs don't know they are operating QRP, even QRPp, even through they use 100W out of their radio. I like to test antennas using 2-3W.. I also suspect any sufficient length of wire is going to work, no matter the configuration. Nothing better than a resonant antenna of course, but a long wire, UNUN and tuner does almost as well, though not quite. Modes make a difference too of course, and one HAM might be happy with his compromise antenna for CW while another calls it garbage for SSB.

I have to this day never seen truly military grade hardware in amateur radio.. Some come close, but no cigar. Anything that says "tactical" or "military" while being sold to the public makes me suspicious. Some manufacturers of military gear do sell to the public, but at prices generally beyond most people's means, even for a simple antenna. My RT-320 used to cost around $15K in the early 80s!

I have seen the resistor terminated antennas before, nothing new.. They do work, but as Bob mentions, they do eat power. I believe they were mostly receiving antennas on low bands to reduce noise.

Convenience has a cost.. Often however, we can obtain much better results by using a resonant antenna, even if we must spend a few minutes more tuning..

But hey, that's why we make and buy a bunch of them right? Choice!

Gil

RadioRay

I have to agree with Gil, in that, many antennas are proof that QRP WORKS. Haha

De RadioRay ...-  .-
"When we cannot do the good we would, we must be ready to do the good we can."  ~ Matthew Henry

Lamewolf

QRPp also works Ray.  I got on 40 meters once with my Yaesu FT-817 and thought the band sounded unusually quiet and then I hear a CQ call that is very clear.  I answer the call because its one I've worked before just to say hello and he is about 30 miles away.  He informs me that I was very weak and gives me a 339 report and thats when I realized the switch on the tuner was set to the dummy load and while he was sending I switched to the antenna and his signal just about blows me out of the chair !  When I returned, he thought I had switched on an amp !  I was running 2 watts !

cockpitbob

LOL, I had a similar experience.  I think those MFJ tuners with dummy loads leak some out the antenna when set to dummy load.  I was just practicing my CQ into the dummy load one day and someone replied.

gil

A dummy load at the end of a long coax cable probably makes a great tactical broadband antenna!

Gil

Lamewolf

To a point Gil the dummy load on the end of a coax will work, but put a coax T fitting on the dummy load, connect the radio to one side of the T and a random wire to the other and it will a lot better because the random wire would not be shielded.  I've actually done this before just to see how it would work and it did better than I expected !

gil


Lamewolf

Quote from: cockpitbob on September 09, 2016, 11:24:44 AM
LOL, I had a similar experience.  I think those MFJ tuners with dummy loads leak some out the antenna when set to dummy load.  I was just practicing my CQ into the dummy load one day and someone replied.

It was an MFJ tuner I was using too !  I even added a binding post to the back panel on one of my MFJ tuners that connects to the dummy load so I could connect a random wire to it.  I use this sometimes when just listening to help cut down on the noise but it works on transmit too.