Question on thru-glass antenna

[KJ4FWA]

Well, to make a long story short, I wanted to listen on my ham radio on the way to and from work, I bought a thru-glass type antenna, (one side sticks to the outside one sticks on the inside etc) It works very well considering on picking up on the repeaters and I hear people talk all the time and the voice is pretty darn clear, my question, and I'm sure it's been answered before... Can these types of antenna be used for transmitting and if so, what kind of signal quality would you expect to see from one of these transmitting on 2 meter ham?

 

[jon_k]

Well, to make a long story short, I wanted to listen on my ham radio on the way to and from work, I bought a thru-glass type antenna, (one side sticks to the outside one sticks on the inside etc) It works very well considering on picking up on the repeaters and I hear people talk all the time and the voice is pretty darn clear, my question, and I'm sure it's been answered before... Can these types of antenna be used for transmitting and if so, what kind of signal quality would you expect to see from one of these transmitting on 2 meter ham?

This depends mostly on the SWR. For many of these antennas the answer is NO.

The air gap creates a point of signal reflection back into the transmitter where the coax is attached to the glass. Not enough of the signal will jump the gap for a good SWR, with a significant portion reflecting back to the radio.

Reflected power is dangerous to the transmitter beyond a specified margin. Contact an amateur in your area who has an SWR meter to test the amount of reflected signal. An SWR meter will be an item you will need to purchase sooner or later as an amateur so you may wish to purchase one now. A local club will have a member who can test your SWR.

 

[Grog]

Providing you can install one (some glass won't work as well) it might work well enough for your needs. They get lots of bad press, but there are some hams who think anything less than a 5/8 wave on VHF is crap (even though those in mountainous areas know a 1/4 wave can actually work better).

I used to work for a guy who had a glass mount scanner and UHF business band antenna, also had a glass mount scanner antenna on the company truck I was issued and while not perfect, it worked as well as anything would for the conditions. He never had a bit of trouble using a 40 UHF radio between 461 & 469 and he had owned a two way radio shop before he was my boss.

When the time came for a ham antenna for his sedan, he went with a 2/440 antenna on the center of the trunk lid. It might have been because he already had two antennas on the rear window and didn't want it to look too crazy

 

[k8tmk]

I used one for a few years on an Astro van. It worked fine, except when the windshield was wet.
The most noticeable effect of a wet windshield was that the SWR would climb, and the RF would then get into the van's computer module. That would cause the engine to slow down whenever I transmitted.

There is an adjustment screw so you can tune the antenna.

Randy, K8TMK

 

[hoser147]

Never used them to transmit, however the local PD here uses them on unmarked cars, for 155mhz.......

 

[zz0468]

It's a compromise antenna with compromised performance. And they work ok, considering.
The trade off is ease of installation and no holes, vs loss compared to a similar sized antenna on a permanent mount. What do you want? You want to get a great antenna? Drill a hole. You don't want to drill a hole? Then don't, but then, don't expect top performance, either.

 

[KJ4FWA]

Well, if it was my car I wouldnt care about drilling a hole. It's my moms van (gets the best gas mileage) and I'm sure she wouldnt want holes punctured in her new to her van.. Is there a clip on type or Mag mount type that would work?

 

[k8tmk]

I'm sure there are mag-mount antennas.

Another solution is to bend a suitable piece of flat metal, screw one end inside the edge of a trunk lip, or hood where it won't show, and mount your entenna on the other end. On my Blazer, I screwed one end of a metal strip inside a tail-light opening and mounted my amateur antenna on the other end. I was even able to route the coaxial cable though a gap between the tail-light and the vehicle and on inside.

For best results, the antenna shoud be mounted in the center of a metal roof so the roof acts like an omni-directional groundplane, but sometimes you have to compromise.

Randy, K8TMK

 

[KJ4FWA]

Well.. On this car there's no trunk, It's a van, An 01 Windstar.. I'll look more into your idea though. It may work for my needs

 

[spiritwolfpr]

Hello Guys:

Well I had one for years and it worked pretty well for me on 2 meters.

 

[Grog]

Well.. On this car there's no trunk, It's a van, An 01 Windstar.. I'll look more into your idea though. It may work for my needs

You have it made, if that van were mine I'd have at least eight NMOs installed within the first week of having it. That's prime antenna real estate

 

[kelltara]

I bought one for my cb once and after going installing it, I found the reception was less than I expected and the swr's were too high to transmit.
I ended up putting my antenna on a hood channel mount on my van, which eliminated the need to drill holes and allowed me to put my firestick back on and increase my range. It is not in the optimal spot for tx or rx but it works alot better than the thru the glass unit.
Check online radio stores like www.kenselectronics.com/lists/ants.htm or others - they have a variety of different mounts for different situations.