Radio Shack 20-032 Transmitting on 2 Meter

[ch40n1k]

Hi there,
I just recently got my ham ticket. I have a radio shack mag mount "scanner" antenna that I use with my scanners. It works as well as can be expected for scanning.

I've also used it a few times with a 2 Meter HT, and it seems to work ok on transmit and receive.

My question:
I just purchased an ICOM mobile 2 Meter radio that I will be using for a base unit. The max output is 65w (Which I'm not planning on using anytime soon) with steps at 25,10 and 5 Watts.

I'm still kinda new ... so be gentle. I don't have an SWR/Power meter yet, but I'm hoping someone here can tell me if I should be ok using the Radio Shack 20-032 Mag Mount scanner antenna to transmit on at no more than 25 watts. I've seen a couple of things on the Internet about modifying the length between the coils etc etc.


If anyone could lend their expertise I would greatly appreciate it.

 

[ermin]

Radio Shack 20-032

I don't think I'd use it for transmitting. Most scanner type antenna's that can be used for the ham bands usually state that in the instructions.

73 Ed

 

[n5usr]

Wow, they still make that? I have one I purchased (wheels grind slowly...) probably 15 years ago! It's no longer "stock" - I butchered it to make it a proper dual-band 2M/70cm antenna.

IIRC, I found that I couldn't get the SWR nice and flat with the stock setup - it must have been too short, because I wound up using the middle rod on the bottom, then the lower coil, then the top rod. Discarded the upper coil and really short bottom rod. After some trimming of the two rods, I wound up with a mag-mount dual-band quarter wave.

Today, I would just buy a pre-made dual-band quarter wave! But it was a fun and satisfying project at the time for a teenager with no money... (Back then I didn't care about low-band anyway, so it still worked fine for scanning as well.)

I can't find any data on how much power those coils are rated for. I seem to recall it was quite low. I only used the thing with a handheld. I wouldn't run a mobile on it at higher power unless you have something that definitely says it'll handle that much.

Edit: Hm... Just did a search of reviews on this antenna, and it is quite evidently not made like it used to be... I found quite a few complaints about the coils not holding up. I can say my 15 year old one is doing just fine, but the new ones have apparently succombed to corporate penny-pinching...

 

[SkipSanders]

I wouldn't try more than 5 watts into this antenna. It's going to have worse than 2:1 SWR, at best.

 

[btritch]

I wouldn't try transmitting with it until I checked the SWR meter. It may be ok but if it's too high you'll ruin the radio. I have found this out from experience. You can get a cheap SWR/POWER meter at either Radio Shack or Ebay. When I say cheap I mean usually less than a $20 bill. I mean it's up to you, If you want to transmitt anyway with it, I'd make sure I used an older radio that wasn't worth much. I wouldn't use a good one, Personally I don't think I would at all but it's up to you.

 

[djeplett]

You can get a cheap SWR/POWER meter at either Radio Shack or Ebay. When I say cheap I mean usually less than a $20 bill.

***BEWARE***

Alot of those cheap SWR meters are meant for CB band with 4 watts transmit only and are designed to cover 3 to 60 MHz tops. To properly test the setup he's talking about you should use an SWR meter designed for the power ratings and frequencies we're talking about here.

I use an MFJ-862 SWR meter that covers 2M/220/440 myself.

 

[jonny290]

***BEWARE***

Alot of those cheap SWR meters are meant for CB band with 4 watts transmit only and are designed to cover 3 to 60 MHz tops. To properly test the setup he's talking about you should use an SWR meter designed for the power ratings and frequencies we're talking about here.

I use an MFJ-862 SWR meter that covers 2M/220/440 myself.

862's a great meter for vhf/uhf; the fact that it's cross-needle just adds to the package.

 

[djeplett]

I just checked the Shack out of curiosity and the only one in stock is designed for CB/HF. 3 to 30MHz and 20W/200W/2000W scale. If you look at the customer reviews you'll see a few people have tried it with poor results. On top of all of that it's $49.99.

862's a great meter for vhf/uhf; the fact that it's cross-needle just adds to the package.

Yep. Don't get me wrong, there are more accurate meters. But at least the 862 is designed for 2M. And if memory serves, I bought mine on eBay for about $40 shipped.

 

[key2_altfire]

In addition to any initial SWR problems, transmitting power can overheat something in the RF path, possibly breaking/burning the conductor similar to how a fuse would blow. Once your antenna burns out, it goes to either open or short circuit, and then SWR flies.

Personally I wouldn't risk it. I'm on my second Icom IC-2200H. The first one I had connected to an HT antenna (rated for 5 watts). I was only transmitting at 5 watts, but somehow the power setting got bumped to 65 without me realizing it. In my case, the antenna shorted, and my guess it was from overheating. Luckily it's only a $165 radio, but heck, an antenna is only like $25!

 

[Bayonne-Bob]

Get an swr meter (or have a friend bring theirs or borrow theirs)
Get a antenna designed for 2 mts (many out there cheep (or make it yourself)

Don't risk your equipment

I am guessing since you are new to your ticket (congrats) that you also are tight on $$
so is best to do it right from the get go

try learning from others mistakes
it is easier (and far cheeper) then making your own mistakes

OH and GOOD you got your Ticket....ENJOY IT !!!