RS 20-006 antenna

[grey4trainz]

Hello,

I recently purchased the Radio Shack 20-006 Telescoping antenna to monitor the railroad band. It received great to fair reviews for what it is. My question is: how do you tune this antenna to listen to 160-161Mhz for the railroad. The instructions say to extend only the top four sections for a broad range of vhf frequencies. Naturally, I do not want every other frequency out there but just that band. I know the formula that states 2800/desired frequency=antenna length. For me, this would be 17" or so. However, it's that load coil on the antenna that doesn't give me a warm fuzzy and leads me to believe this calculation would not be accurate. Any assistance would be appreciated since I can't find much on the net concerning tuning of this particular antenna.

Thank You,
M. Grey-Lexington

 

[gewecke]

Try googling the model number,you get more info. I have that antenna,and it is also designed to transmit on. Don't worry about the coil. Extending the sections gives you an approximate length for the antenna to be resonant in different parts of the spectrum.
If you're just receiving then it should work fine,all the way from 25mhz. to 1296mhz. For uhf for instance,push it all the way down,with only the bottom 3 sections out. For the railroad band,only the top four sections should be pulled out. Hope this helps you!
N9ZAS.

 

[scanner92us]

I found this antenna works best on high band by extending it fully, then lowering the section just above the coil about halfway in. Leave the other sections extended. Works great for me on most of high band.

 

[gewecke]

There's a lot of mixed results from people,that I've read on this thing. I use mine to transmit on 220mhz.with my kenwood TH315. I haven't tried it with a scanner yet.
N9ZAS.

 

[nanZor]

The instructions say to extend only the top four sections for a broad range of vhf frequencies. Naturally, I do not want every other frequency out there but just that band.

I placed this antenna on an MFJ analyzer and they are correct, but for years I was collapsing the top elements wrong.

For 160mhz rx-only operations, collapse all the bottom elements.

For the top element, collapse the lowest above the coil (the fattest top element) down into the coil. This is important.

I got about a 2:1 swr on it with a resistance of 49, and reactance of 27.

For many years I was just collapsing all below the coil section, and then collapsing the top sections to just 4 elements, but was collapsing the skinniest first. This wasn't optimal. Extend all the top elements, and the push the fatty down into the coil.

 

[gewecke]

Yeah,way back when...I almost got to see a brawl,caused by three fella's loudly disagreeing about the impedance factors of this antenna at a club meeting! I thought the guy with the 20-006 was gonna use it as an ASP! I guess I'll have to experiment with mine on different bands some more!
N9ZAS.

 

[grey4trainz]

RS20-006 antenna

Thanks guys,

I have a pretty effective dipole built specifically for this band but it is highly immobile of course. This 20-006 antenna should give me more mobility (once I learn how to use it). I will try the advice "y'all" gave and see what happens.

grey4trainz
Lexington, KY

 

[CLynch7]

Technically, receive antennas don't need to be resonated like transmitting antennas. You're probably going to do the best by just experimenting with it. I've got two for my scanners, and it is rare that I use them in any other configuration than fully extended, but your mileage may vary.

Also, location, location, location! That is another variable, how close/far from the trains you are.

 

[nanZor]

I couldn't agree more - for rx-only work I run antennas on vhf that can get up to about 5:1 without any noticeable loss on long runs of RG-6.

However, on UHF, and especially 800mhz, the additional loss caused by a high swr at the feedpoint when coupled to a lossy transmission line can really add up very quickly - so even for rx-only at 800 mhz (and to some extent at uhf), the marriage of low swr at the feedpoint and low-loss feedline becomes extremely important.

 

[WQDL753]

I got the 20-006 for my pro-95 years ago. I found that it always did best full out, the most imprtant thing is location as it's been said before. you can get a huge diferace just by moving it 2 inches. I've even used it as a directenal by holding the scanner at waist level with the antenna about 6 inches infront of my chest and turning around slowly untill i got the best signal. And I just went through it again with another telescoping antenna, I found a signal, pushed it down to the recomended lengh to improve it, and I lost 2 full bars from what I had full out!