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Re: Mast mounted preamps - I'm a believer!



I've been a believer in preamps since I put one on my 70cm antenna as 
well.  They make barely readable S3-S9 every time!

Dave

At 07:13 9/18/00 -0500, you wrote:
>Hey guys,
>
>Well, this weekend, I finally took a break from most of my household chores
>and finished construction and installation of my mast mounted preamps (Gotta
>get ready NOW for P3D!).  It's a homebrew project I started last spring.
>The amps are an ARR GaAs Fet on 2m and a Down East Microwave GaAs FET amp on
>432 MHz.  The voltage regulation and relay circuits to switch the amps in
>and out on TX/RX are my own design.
>
>I knew the amps added a lot of signal gain as I'd tested them out in the
>shack.  But they also added a lot of increased noise after about 60 to 70
>feet of 9913.
>
>So yesterday afternoon, after kluging a way to secure the amps and heatsink
>into the waterproof housing (secured with bubble wrap stuffed between the
>housing walls and the heatsink (The amps, relays, voltage regulators, etc.
>are mounted on the heatsink)), I mounted the box about 7 feet up my mast (as
>far as I could reach and still easily disconnect things).  It's not ideal as
>I still have probably 20 feet or more of coax between the antennas and
>preamps.  I have a Yaesu G5000A (I think that's the number) El rotor I
>picked up at Dayton that I plan on putting up next spring (no time now -
>getting married in less than 4 weeks!).  I'll also replace my fiberglass
>tube with a solid rod at that time.  It's a Radio Shack telescoping mast so
>getting the antennas down won't be that hard.  Well, OK, yes it will!
>
>OK, the point of all this is WOW!  Do these things work!  I was able to copy
>UO-14 on a very, very low elevation pass and work several stations.  The
>pass really got no higher than about 10 degrees.  It was pretty cool to hear
>just a couple of stations on the bird at the start and end of the passes.
>Signals were easily 59 plus with the preamps.  They were about 51 to 52
>without.
>
>Then I talked to myself on FO-29 for a while.  It was also a very low pass
>and signals were good again.  I probably wouldn't not have been able to copy
>near as much without the amps on.  On the next pass, I managed to work about
>4 or 5 stations, a couple when the bird was getting very close to the
>horizon.
>
>So I am a believer!  Mast mounted preamps work great.  I would say they are
>a necessity!
>
>I've got one minor snag with these guys though.  When I have the preamps
>turned OFF and key the rig my power amplifiers on, the PTT line sticks and
>the amps stayed in TX mode.  The preamps and amplifiers are both controlled
>by the PTT line.  Things work fine with the preamps on, but again, the
>amplifiers stick with the preamps off.  I wasn't able to measure voltages
>since my VOM is at my fiancée's place for something.  I'll get that an
>troubleshoot tonight.  But does anyone have any ideas?  The PTT lines going
>to the preamps pull down a ground line on reed relays that switch voltage on
>and off to the preamps and RF relays.
>
>I took pictures of the box and once developed, I'll send them to K5OE or
>whoever has the homebrew website.
>
>73,
>
>Jon
>NA9D
>
>-------------------------------------
>Jon Ogden
>NA9D (ex: KE9NA)
>
>Member:  ARRL, AMSAT, DXCC, NRA
>
>http://www.qsl.net/ke9na
>
>"A life lived in fear is a life half lived."
>
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