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Re: FT-736 Slow output.



In a message dated 98-05-28 21:06:54 EDT, smithr@mail.gisco.net writes:

> I stumped Yaesu tech support with this one.. I'm currently using an Ft-736
>  with a Mirage B 3016 G amp.
>  When the amp is off line, the transmitter (2 mtrs)achievs full output power
>  at the normal rate. When the amp is 
>  online, it takes about a second for the transmitter to achieve full output
>  power, and doesn't increase at a constnat rate. .Any ideas out there ???

Hi Ron,

In the three years I've own my 736R, I've struggled with this problem from
time to time, both on satellites and in VHF/UHF contests. Here's what I've
done to finally cure it. ** Your Mileage May Vary **

First off, make sure you hard key any external amps!

1  I checked the AFP (automatic final protection circuit) in the offending
transmitter section and set it for spec according to the Tech Service manual.
I have the instructions here as a text file if you need them. Results were
marginal.

2  I cut a specific cable (for lowest VSWR) to go from the 736R to the brick
making it a multiple of 1/2 wavelength of the frequency I most wanted to
operate. The formula used was 5904 divided by the Frequency in MHz, then
multiply by the Velocity Factor of the coax used. The number arrived at is in
inches and is to the tips of the connections.  Results again were marginal.

3  I built and installed OH5IY's TX Delay Mod. This is a neat circuit that
allows you to set a time delay before the rig will generate RF. Thus, all your
external relays etc can switch, then RF comes on. It's a simple sequencer. I
have it set for ~150 milliseconds. Results were Great! It solved 95% of my
problems. But..... while contesting, I discovered another problem.

My 736R has a problem I've never seen anywhere else. This problem only happens
on 2M, and only near band edges. (Like 144.200! arghh) It doesn't happen on
222, 70cm or 1.2G. If you key up the rig with any audio present on the mic, it
will spike the ALC causing it to go full scale and the AFP will take over and
cut back the transmitter. I searched for months to find this one. I have yet
to find the exact cause, but here's what I finally did to solve it.

4  I installed an audio sequencer. I used the TX LED on the front panel to
control a normally closed time delay relay across the first audio amp. It does
essentially the same thing that the OH5IY TX delay mod does, except for audio.
It's set for ~ 100 milliseconds. This solved it!!

Why didn't I just sell the rig? Or take it out back of the shack and shoot it?
It's probably because I hate being beaten by a piece of hardware :-} Plus it
has the muTek mods installed on 2M and 70cm and hears _real well_, and I like
the way it operates on satellites plus it's perfect for our Contest Rover
setup. You get the picture....

Hope this helps.

73,
Mike, N1JEZ
AMSAT #29649
"A closed mouth gathers no feet."



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