One of the things I never saw asked... are any of your
Jumpers the LMR-400 type coax? One of my LMR-400 train
wreck stories started with a Wacom Duplexer and a jumper
of the mentioned. The story ended when I replaced the
jumper with rg-214
just curious...
s.
> "blisswheeler" <[EMAIL PROTECTED]> wrote:
>
> I really appreciate all of the comments on my duplexer mystery.
>
> I made sure everything was tuned properly and took it back to my
> friends home location. We put it back on the air and experienced <2db
> of signal desense with an output of 15 watts. That still doesn't
> duplicate the results of the dummy load test, but that's a far cry
> from the 30db I was experiencing here at my home shop. Some of the
> things I did learn from the experience was that:
>
> 1. Though an antenna may only have a 1.5 SWR doesn't mean that the
> antenna is a 50 ohm match. Using my MFJ ("Mighty Fine Junk" which, by
> the way work pretty darned good, but not in a high RF environment)
> antenna analyzer, the antenna that gave me the most difficulty
> presented an 80 ohm load. The SWR was 1.5. A discone antenna worked
> the best and it presented a 55 ohm load with a 1.2 SWR.
>
> 2. Double shielded coax is a must in repeater operation. I
> experienced this first hand. I had one short jumper I thought was
> double shielded and was not which caused an intermittent such that one
> time it worked into a dummy load and the next it went flaky. Moving
> the coax with the repeater transmitter keyed revealed the culprit.
Use hardline or double shielded coax. Hardline to the antenna is very
> important.
>
> 3. Bench testing duplexers into a dummy load may not duplicate the
> results experienced with the antenna.
>
> 4. In theory isn't necessarily the same as reality. I suppose if you
> know all the variables the problem can be calculated and identified,
> but there are a lot of unknown variables when working with RF.
>
> 5. The environment your repeater is in can cause you to loose your
> hair. Yes it is related to the rf generated, no not because of the
> health effects but because it makes you tear your hear out trying to
> identify a problem.
>
> 6. I learned about whiskers in GE Mastr II receivers... I experienced
> their effects and how to fix the problem, though maybe for only a year
> or two, but I learned to to disassemble and retune the receiver.
>
> 7. Your experienced Techie RF friends are a great help. I have three
> good friends that gave me a lot of ideas and helped me trouble shoot
> this problem. The folks here on Repeater-Builder gave me some good
> tips which pointed in the right direction as well, for that I thank
> you all.
>
> Respectfully,
> Bliss
>
