Antenna Question ( Again )

KG4LHQ · Post by **KG4LHQ** » Fri Mar 17, 2006 1:26 am

Hello,

I have decided that I am going to upgrade my current radio to cover both Public Safety and Ham. As I am on Fire Department and a Ham Radio Op. I am looking at getting a TK-760G or a CDM1250 25 or 45 Watt Model. I have an 04 Silverado 4wd Regular Cab Truck. My current install is a Jetstream 5/8 Dual Band Mobile. The antenna is mounted on my truck bed on the drivers side. I run about a 1.5 SWR on 146 and like a 4 on 154 LOL.

I am looking at getting a Antenex 5/8 Wave or ComTelCo same kind.

Would I lose performance with getting one of them antennas and mounting them on an L bracket on my truck bed with the NMO Antenex Brand Coax? Would you anticipate any problems?

Drilling is not an option!!!

Thanks
John

k2hz · Post by **k2hz** » Fri Mar 17, 2006 4:58 am

A 1/4 wave magmount on the roof is your best option if you absolutely will not drill. Anything in the truck bed is bad. Match and antenna pattern will be poor.

KG4LHQ · Post by **KG4LHQ** » Fri Mar 17, 2006 5:12 am

I've tried a 1/4 Wave on the Roof and it messes with my stereo bad and it makes my speakers do nothing but squeal.

NCSHP311 · Post by **NCSHP311** » Fri Mar 17, 2006 6:10 am

Try a 1/4 wave on an L bracket mounted on the hood grove that would work pretty well! I have one on my 2002 Dodge Dakota with no problems.

KG4LHQ · Post by **KG4LHQ** » Fri Mar 17, 2006 6:51 am

I have tried both on the roof using a magnet mount and on a lip mount secured to the engine hook with the coax running thru the firewall. It doesn't do any good it makes my FM Radio speakers squel a very high pitch tone that I'm surprised doesn't bust the speakers. So thats why I've used the 5/8 Wave on the Truck Bed. It never did it with it.

va3wxm · Post by **va3wxm** » Fri Mar 17, 2006 8:19 am

5/8 dual band? As in VHF and UHF?

If you don't use UHF it'd be better to get a single band antenna for VHF.

I don't have any experience with the Antenex brand but my Larsen NMO150 has a pretty wide bandwidth.

I also have a Larsen NMO150HW (1/2 wave) and it's even wider. It's currently mounted to a drilled NMO on the trunklid and has a 2:1 bandwidth of almost 30 MHz.

RadioSouth · Post by **RadioSouth** » Fri Mar 17, 2006 9:23 am

Did you check the SWR on those setups causing your stereo to howl ?
Prime indicator although not absolute.

Tom in D.C. · Post by **Tom in D.C.** » Fri Mar 17, 2006 12:19 pm

If you check the claimed bandwidth of various 5/8 antennas you'll probably find
that it's about 6 mHz, so if you want to be under 2:1 on 146 mHz and under
2:1 at 154 mHz you're probably asking what the antenna can't do, or at least it
can't do it with decent SWR of less than 2:1.

Several companies make inexpensive duplexers that would allow you to run
two antennas from the same RF output on the radio, so you could still run separate VHF and UHF antennas, plus you might have a better matchup on VHF.

captrgm · Post by **captrgm** » Fri Mar 17, 2006 6:05 pm

You should try the NMOWB150BK antenna mount made by Radiall/Larsen. It will give you a 20 Mhz bandwidth with matching circuitry in the base of the antenna. I have seen good results.

KG4LHQ · Post by **KG4LHQ** » Fri Mar 17, 2006 7:07 pm

Well I really didn't want to spend $80 on an antenna. I do not want to drill a hole and I dont' want a huge antenna on my roof so therefore I thought using it on the truck bed would be fairly adequate without looking gauky. From what I understand the pattern on the antenna and effectiveness will be low if its installed on the truck bed behind the drivers door currently where I have my antenna now.

I feel I could go with a 35 - 45 dollar Antenex 5/8 Wave antenna or a ComTelco and I would use a 1/4 wave on the roof with a Magnet Mount but due to everytime I key my radio it makes my speakers make a high pitch squeal I can't stand it.

Any other suggestions on how to fix that problem or what I can do - I am on a budget restriction.

BTW - I know you get what you pay for. LOL

KG4LHQ · Post by **KG4LHQ** » Fri Mar 17, 2006 7:08 pm

http://cgi.ebay.com/ANTENEX-VHF-3-DB-GA ... dZViewItem

This is the antenna I've pondered about getting its a 5/8 Wave Antenex VHF w/ Spring..... But if you feel that it wont' do worth anything by mounting it on the truck bed then I'll have to do something else.

W6JK · Post by **W6JK** » Fri Mar 17, 2006 8:37 pm

Rather than compromise your antenna installation to accomodate a cheesy stereo, why not fix the stereo instead? I think I'd start with ferrite filters on the speaker leads, and then filter the DC power leads.

KG4LHQ · Post by **KG4LHQ** » Fri Mar 17, 2006 10:10 pm

Well I really didn't want to take all the radio out and mess with taking the door covers off to put little ferrite beads on the door wires. If I have to I will but I really would rather not.

I know you all are trying to help me out and I appreciate that. I will try the 1/4 wave antenna on the roof again and fool with it...

W6JK · Post by **W6JK** » Sat Mar 18, 2006 8:27 am

You probably don't need to open the door panels, unless the audio amplifiers are there. The idea is to keep RF on the speaker leads out of the radio, so you need to put the filters at the radio. It's no fun working under the dashboard either, but at least it's all in one place.

wa2zdy · Post by **wa2zdy** » Sat Mar 18, 2006 9:42 am

It sounds like you don't want to take the steps that MIGHT help you, you don't want to spend "too much" money and you don't want to install the antenna correctly (with a hole.)
As such I think you may soon be on your own with this.

The SWR problem would be migated by tuning for minmum SWR on a frequency approximately midway between the desired frequencies. Of course this may not be ideal as Tom said above but . . .

Good luck.

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