[Amps] Alpha 77 160 meter plate choke

[Carl]

The RFP RFC-3 is the Ameritron for $5 more

The 77DX started with the B&W 800 and then the 801 to improve 160 once 
people started getting serious about the band.
Later the 802 was used by many to allow WARC's.

Ive used the Ameritron in several 77DX and SX after the final tapered design 
proved reliable. Another that looks similar and goes back to the 80's is the 
one in the TL-922/922A; Ive used several of those that were removed during 
6M conversions.

AFIK is was one of the senior tech guys at the ARRL that came up with that 
concept back in the 70's or so.

Carl
KM1H




----- Original Message ----- 
From: "Paul Christensen" <w9ac at arrl.net>
To: <amps at contesting.com>
Sent: Monday, March 24, 2014 4:46 PM
Subject: Re: [Amps] Alpha 77 160 meter plate choke


> Tree,
>
> You may want to check for any in-band resonances if you haven't already. 
> In my 77Dx, I've also added additional C  from +HV to ground.  For the 
> upcoming 77D project, the plan is to discard the B&W 801 choke and replace 
> it with an RF Parts RFC-3.   This choke should provide ample 160m 
> inductance and is stagger-wound to minimize or eliminate in-band resonance 
> but needs to be validated after installation.  Specs are:  1.5A, 225 uH, 4 
> KV max.
>
> Paul, W9AC
>
>
> ---- Original Message ----- 
> From: "Tree" <tree at kkn.net>
> To: <amps at contesting.com>
> Sent: Monday, March 24, 2014 2:17 PM
> Subject: [Amps] Alpha 77 160 meter plate choke
>
>
>> All -
>>
>> I have made a mod to my Alpha 77 to add about 60 uH to the RF plate choke
>> when on 160 meters.  I originally was going to mount a switch to control 
>> a
>> HV relay - but came up with a better solution.  If you are interested in
>> knowing more - check out the pictures here:
>>
>> http://www.kkn.net/n6tr/directories.html
>>
>> Look under Alpha 77Dx.  The relay was purchased from Henry Radio.  It has 
>> a
>> 26.5 volt coil which seems to work just fine off of the +24 volt 
>> regulated
>> power in the amp.
>>
>> I added a 4700 pf 6KV cap from the HV to ground which you can see in the
>> pictures.
>>
>> I am not sure this makes a big difference - but I certainly feel better
>> about using the amp on 160 with this mod.
>>
>> 73 Tree N6TR
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>
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