FW: [Alinco] DR-130T roasted RF module?

[Bill Kuhn - MCSE]

=20
I had been wondering if these had any protection from antenna mismatch
or not. I guess I found out the hard (and dumb) way.=20

My homebrew copper pipe dipole had nice low SWR when we put it up, but
I'm sure that wasn't the case when it had almost half an inch of ice on
it for a couple of weeks.

I guess I really ought to quit being so cheap and invest in a VHF
watt/SWR meter so I have a clue what is going on out there..

73
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Bill Kuhn
KC0NYL

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_____________________________
 -----Original Message-----
From: Eric Lemmon [mailto:elemmon@impulse.net]=20
Sent: Sunday, February 15, 2004 12:13 PM
To: Bill Kuhn - MCSE; Alinco@mailman.qth.net
Subject: Re: [Alinco] DR-130T roasted RF module?

Bill,

Yes, you probably have a toasted RF PA module.  Both the DR-119T and the
DR-130T radios use the S-AV17 PA module, which costs about $55 from RF
Parts.  But, before you replace the module, check to see that the driver
stage is providing a signal to the module.  You can download the DR-130T
service manual at:

http://www.alinco.com/pdf.files/Service/dr130ser.pdf

These modules have absolutely no protection from impedance mismatches
and high SWR, and they are notorious for erratic source impedance.=20
Ironically, they are more likely to fail when operated at low power
levels since an insufficient drive level causes the module to fall out
of Class C operation, greatly reducing its efficiency.  An impedance
matcher installed as close to the radio as possible will improve the
match between the PA and the antenna.  Depending upon the drive level,
the PA's source impedance is probably far from 50 ohms.

73, Eric Lemmon WB6FLY

Bill Kuhn - MCSE wrote:
>=20
> I have a DR130T that has apparently roasted its RF amp module... It's
kind of odd - Now whether the radio is in low or high RF setting it
draws under 3A (my DC supply has an accurate ammeter). The built-in RF
meter still indicates a low power output on LOW, and a high output on
high. It does this on my antenna and on my dummy load. On-air testing
shows no signal difference between power levels at all. This radio
always drew right at 10A before this happened... Anyone know if this is
typical of a toasted RF module?...