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Author Topic: VHF/UHF mobile remote swr meter?  (Read 1974 times)
WB9YCJ
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Posts: 280




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« on: October 20, 2009, 05:06:52 PM »

My vhf/uhf triband radio main body is trunk mounted and the control head is up front and gives no indication of swr or swr fluctuations.

Im looking for an vhf/uhf equivilent to the
Comet CMX-1 remote swr meter so I may install the sensor at the output of the transmitter (trunk mounted) and have the indication up front.

No, I do not want to change radios. Ideas?

Thanks, Ken
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K5LXP
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« Reply #1 on: October 20, 2009, 08:18:45 PM »

I'll stick my neck out here- why do you want to watch an SWR meter reading that will never change?


Mark K5LXP
Albuquerque, NM
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KC7YRA
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« Reply #2 on: October 20, 2009, 08:46:44 PM »

I do not know of any currently available product that will do this on the VHF stuff.

I really do have to pose the question (as Mark did) of why?  If you say "because", then I will accept that as every ham has their own criteria of how they treat their equipment.  I do think it may be anti climactic as the SWR will most likely never change.  If you notice a degradation in performance one day then you can slap a meter onto the antenna and check it out.

But the world of mobile antennas is pretty bomb proof.  I have multiple antennas and I never worry about the SWR suddenly changing nor have I ever had it happen save for a few times I have heard thuds as the antenna was taken out by low hanging trees (Had a Maxrad coil explode from contact with a low tree branch at a very very cold temp).

It was painfully obvious however as I heard a huge BANG and I was unable to get into the repeater any more.  Modern radios will protect themselves so I did not feel too bad about giving the mic a tap to confirm my suspicion.

Brad
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WB9YCJ
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« Reply #3 on: October 20, 2009, 10:58:37 PM »

Why one might have the luxury and benefit of a vhf/uhf reflectometer on duty in a mobile in motion situation ?  

Last nite as I drove from Anaheim to San Diego, I heard only a few 223 Mhz signals and they seemed a bit weaker then should be. Tuned down to 220 Mhz business band - same thing - no sigs. Seemed strange.

>>>> I was wondering what was going on ?? <<<<

I was using a Hustler cgt-220 (finest gain type 220 mobile ant) with one of their (Hustler) trunk lip mounts which has a goofy motorola plug/jack quick disconnect in-line (which is Hustler factory installed). They have had these QDs on their trunk lip mounts for years.  

I do not like the idea of having coaxial Q.D. connectors in-line (factory installed or not) with mobile antennas - they can offer possible opportunities for corrosion, intermittencies, bad connections, uncertainty, etc.

(Recently, I noticed a new in package Hustler trunk lip mount at HRO Anaheim without the QDs. Perhaps Hustler (Miserable Wells, Texas) wised up?)

Anyway, at the time I was driving, I had no solid idea why I wasnt hearing more signals on the band. Driving at 70 Mph, I didnt want to stop and start checking connections, coax, antenna integrity, and things. This is where I wanted the benefit of having a swr indication available to me from the drivers seat. Later, I learned that the reason I was not hearing much was 220 Mhz INACTIVITY (at that hour of the evening).  

I like the idea of having a reflectometer in this situation much the same way I put a smoke detector in a room thats not supposed to have a fire.

I understand many vhf/uhf  transceivers have foldback circuits BUT I prefer to avoid that situation - i.e relectometer on duty.
This is a personal preference.
I still wish Comet had a V/Uhf version of the CMX-1 (HF).

Ken
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K0BG
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« Reply #4 on: October 21, 2009, 05:55:00 AM »

I'll take a different tack here.

First, if you want good, overall performance, you'll drill the necessary hole(s) and dispense with the clip mount. As you've discovered, clip mounts are short on ruggedness and reliability.

Next, while gain can be important in isolated cases, selecting an antenna based solely on its advertised gain figure is playing the gain-game, and a game you'll always lose! In fact, if the main communications path is through a repeater, less gain is often preferred. It all has to do with the HAAT of the two ends of the communications path.

Multiband VHF/UHF mobile antennas are always a compromise, not matter how you cut it. This is especially true of the Comet multiband. If they were as good as they're supposed to be, you'd see public service vehicles using them. You don't, and that fact speaks volumes.


Alan, KØBG
www.k0bg.com
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K5LXP
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« Reply #5 on: October 21, 2009, 06:55:18 AM »

> I wanted the benefit of having a swr indication
> available to me from the drivers seat.

This is a curious reason.  Given that:

> I didnt want to stop and start checking connections,
> coax, antenna integrity, and things.

So at best, an SWR meter might tell you something is horked, but you're probably not going to be in a position to do anything about it anyway.  So the end result is the same.  What's the point?

As Brad and Alan point out, if you have a robust installation the only problem you may ever encounter is an outright mechanical or electronic failure.  An SWR meter can only provide a reactive response, i.e. you only know about a failure until after it happens.  Simple physical inspection and maintenance is proactive and may prevent a failure in the first place.  A meter merely adds expense, is one more thing to mount, route wires for, and adds more connections. It does not make the system more reliable in the end, maybe even less so.  It amounts to being a fault indicator which is superfluous, since won't tell you anything you don't already know just by operating the radio.  Instead of a meter, spend the money on wire loom to protect the cabling, tie wraps to secure them, quality connectors, a sturdy mount and a proven antenna.


Mark K5LXP
Albuquerque, NM
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WB9YCJ
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Posts: 280




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« Reply #6 on: October 21, 2009, 07:39:55 AM »

Mark and Alan,
I already realize and understand all the things in your responses to me.

Example: I ALREADY understand that trunk lip mounts are "good" when installed properly but can offer possible problems. They are seldom if ever  seen on professional installed public service mobile installations.

Example: I ALREADY understand robust mobile installation benefits - drilling holes in cars (ugh) , wire looms, cable ties, etc

No, I do not "need" a v/uhf reflectometer.

Im removing the smoke detectors in my house also.

Ken
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W0FM
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« Reply #7 on: October 21, 2009, 12:46:18 PM »

Hi Ken.  It doesn't souund like anyone on here is apt to change your mind on your request, but I feel a need to present some analogies.

Your home's smoke detector alerts you early to the fact that you have the beginning of a problem so you can take proper action to maintain the safety of your family.

An SWR-Meter on VHF/UHF will "usually" only alert you to an antenna failure.  Much more drastic.

I've been in the commercial two-way business for 37 years dealing with "life and death" public safety communications and I have NEVER seen a mobile radio with an external SWR meter to monitor the antenna system.  Just not necessary.  If it were, all police and fire radios would be installed with one.

Again, not likely to change your mind if your heart is set on strapping an SWR Meter under your dash, but I had to say it.

Good luck,

Terry, WØFM
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KC9BUH
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« Reply #8 on: November 01, 2009, 04:19:11 AM »

Kenwood use to make remote vhf/uhf swr/pwr meters.You will have to look around to find one.I hope this answers a part of your question.
Mike
KC9BUH
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WB2WIK
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Posts: 20542




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« Reply #9 on: November 01, 2009, 06:29:52 PM »

The common Bird 43 Thruline allows you to "remote" the directional coupler and put the meter anywhere you want.

It comes with only about 9" of coax interconnecting the coupler and the meter (indicator); however this cable is only handling 30uA DC current and can be extended as long as you want -- I've run them for 30 feet or so, with no problems at all.

The Bird 43 has elements good to 3 GHz.

WB2WIK/6
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