[VHFcontesting] Mirage amp problems

[Rusty Boling]

Ok guys...some more details on this....Hooked the amp and rig to some deep cycle batteries and still getting the same problem (so wasn't the supply).  I also tuned around to find higher and lower SWR points to see if SWR had an effect on the distortion....Well I found out that the distortion is actually worse with a lower (1:1) SWR than a higher one (1.5:1).  That seems unusual to me but oh well.  The comments that I am getting from most of you via direct email seem to lean towards the final transistor(s) biasing.  I do not have a schematic and can't find one so far (bought it used).  How would I go about setting the bias if any of you are familiar with the design of the B1016 from the 80's I am guessing.  Is there anything in the input circuitry that could have changed that I could adjust or replace?  Like I said, power output is good.  For some reason (on FM atleast) it only take about 2-3 watts to get 160W out.  I know there is a power curve, but newer Mirage amps that I h
 ave seen
 are not quite this aggressive, which makes me wonder if some of the input circuit is to blame...Any more guesses???   Rusty  NE4ME
 
 

Message: 1
Date: Sun, 7 Nov 2004 09:01:37 -0800 (PST)
From: Rusty Boling 
Subject: [VHFcontesting] Mirage Amp problems
To: VHF CONTESTING 
Message-ID: <20041107170137.92603.qmail at web50302.mail.yahoo.com>
Content-Type: text/plain; charset=us-ascii

Having problems with an older Mirage B1016 2M 160W amp for a while now. Getting reports of distorted audio at all power levels on SSB. Output power is still good. Distortion still there even with low drive power and low mic gain. Does not have the problem on FM and I don't know about CW (havent checked that yet). Driving the amp with a IC-271A usually and occasionally with an IC-706MKII. I am guessing the amp is 15-20 years old now and the reports of it beginning to become distorted have happened over the last year or so. I have eliminated low voltage, RFI (for the mostpart), and poor connection to power supply. I spoke to K4TO last night and he thinks it could be a bias problem within the amp. The only thing that I could do to check that was compare readings between the 2 high power transistors. All voltages on the transistors were consistant with eachother per given power input and output according to my DVM, not that I like 160W on 2M at an armlength away. Anyon
e have
this same problem before and was able to resolve it? I'd hate to resort to making it FM use only. Any ideas??? Rusty NE4ME

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End of VHFcontesting Digest, Vol 23, Issue 5
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