[Amps] Amps Digest, Vol 82, Issue 34

Sun Oct 18 07:36:06 PDT 2009

Thanks Peter for the interest and the tips

I am working on it and I hope to have a solution on it..
Thomas give me some tips witch I use now to make some pre eliminary
measurements to see what happen and what is wrong on it..!!!
About the C1-C2 capacitor pF-values it is not easy for higher bands we need
small values and for the lower bands we need big pF-values.
I now about padders for different band covering,but this needs a ceramic
bandswitch with at least 3 wafers
1 wafer for C1 pads
1 wafer for the coil himself
1 wafer for the C2 pads
Not easy to find,and when you find one it is mostly bigger than my whole PA
stage and costs a lot..
Maby you have a big personal stock,so you can help my further on that
particular way hi hi,little joke Peter..
You now what I mean it is not easy at all,surely not in Belgium to find
something usable for that use, and with dimensions I can bild in ...!!
I am working around,I hope I can find the solution for what I have for the
moment,especially for the higher bands.
I already put some more coils into also.
I hope it is also a solution,because I was starting with a
correctPI-calculation with give me a solution with very small turn
values,but this seems to be praticly not realisable,or a big fault.
Maby possible when you have no stray and so on and so on !!!

Regards Jean.

----- Original Message ----- 
From: <amps-request at contesting.com>
To: <amps at contesting.com>
Sent: Saturday, October 17, 2009 9:00 PM
Subject: Amps Digest, Vol 82, Issue 34

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> Today's Topics:
>
>   1. Fw: 8874 Pulls (Joe Dube)
>   2. 8875s needed (n8de at thepoint.net)
>   3. Re: Fw: 8874 Pulls (Paul Playford)
>   4. Re: HELP...2x GS35b (DF3KV)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Fri, 16 Oct 2009 16:08:52 -0400
> From: "Joe Dube" <jdube1 at bellsouth.net>
> Subject: [Amps] Fw: 8874 Pulls
> To: <Amps at contesting.com>
> Message-ID: <BD804F776ADF4C2498AD3BD9B7696FBC at JoeDubePC>
> Content-Type: text/plain; format=flowed; charset="iso-8859-1";
> reply-type=response
>
>
>
>> Several weeks ago there was inquiry about 8874 pulls.  There was
>> information about someone who had access to medical pulls and was selling
>> them. Does anyone out there remember the url or the address of the
>> gentleman that was selling these tubes???  Thanks for any help you all 
>> can
>> give.
>>
>> Joe Dube K4TR
>> K4TR Antenna Mfg & Sales
>> www.k4tr.com
>> 352-232-0281
>
>
>
> ------------------------------
>
> Message: 2
> Date: Fri, 16 Oct 2009 16:37:27 -0400
> From: n8de at thepoint.net
> Subject: [Amps] 8875s needed
> To: Amps at contesting.com
> Message-ID: <20091016163727.qfu6rs0f4g8o0g84 at webmail.win.net>
> Content-Type: text/plain; charset=ISO-8859-1; DelSp="Yes";
> format="flowed"
>
> A friend in UAE has a MMLA2500 amp which needs a couple 8875 tubes.
>
> Anyone have pulls for sale or, perhaps, a source for same?
>
> Thanks
> Don
> N8DE
>
>
>
> ------------------------------
>
> Message: 3
> Date: Fri, 16 Oct 2009 13:48:20 -0700
> From: "Paul Playford" <paul at w8aef.com>
> Subject: Re: [Amps] Fw: 8874 Pulls
> To: "Joe Dube" <jdube1 at bellsouth.net>, <Amps at contesting.com>
> Message-ID: <3832B5CDF36E4FDA925809B0CBF953BF at W8AEF>
> Content-Type: text/plain; format=flowed; charset="iso-8859-1";
> reply-type=original
>
>      To:  "Amp Reflector" <amps at contesting.com>, "heathkit reflector"
> <heathkit at mailman.qth.net>
>      Subject:  [Amps] 8874 pulls
>      From:  "kingwood" <k5jv at kingwoodcable.com>
>      Date:  Mon, 21 Sep 2009 12:43:58 -0500
>      List-post:  <amps at contesting.com">mailto:amps at contesting.com>
>
> Greetings to all,
>
>        I have two sets (total of four) 8874's pulled from working Alpha
> amps that were converted to 3CX800's.  These are probably the last 8874
> pulls that I will have as I will no longer make the conversions.  Will 
> sell
> in sets of two, or all four together. Sets of two, $400.  All four  $750. 
> I
> will pay shipping to original 48.  Trades will be considered for Ameritron
> QSK-5, QSK-5PC, or original HeathKit QSK boards.  Can deliver to Belton.
>
> 73 de Lon, K5JV
>
> 1110 Golden Bear Ln.
> Kingwood, TX 77339
>
> 281-358-4207
> 281-358-4234 FAX
> 281-795-1335 CELL
>
>
> ----- Original Message ----- 
> From: "Joe Dube" <jdube1 at bellsouth.net>
> To: <Amps at contesting.com>
> Sent: Friday, October 16, 2009 1:08 PM
> Subject: [Amps] Fw: 8874 Pulls
>
>
>>
>>
>>> Several weeks ago there was inquiry about 8874 pulls.  There was
>>> information about someone who had access to medical pulls and was 
>>> selling
>>> them. Does anyone out there remember the url or the address of the
>>> gentleman that was selling these tubes???  Thanks for any help you all
>>> can
>>> give.
>>>
>>> Joe Dube K4TR
>>> K4TR Antenna Mfg & Sales
>>> www.k4tr.com
>>> 352-232-0281
>>
>> _______________________________________________
>> Amps mailing list
>> Amps at contesting.com
>> http://lists.contesting.com/mailman/listinfo/amps
>
>
>
> ------------------------------
>
> Message: 4
> Date: Fri, 16 Oct 2009 23:58:38 +0200
> From: "DF3KV" <df3kv at t-online.de>
> Subject: Re: [Amps] HELP...2x GS35b
> To: <amps at contesting.com>
> Message-ID: <1Myuot-1R6we80 at fwd06.t-online.de>
> Content-Type: text/plain; charset="iso-8859-1"
>
> Hi Jean-Pierre,
>
> The output Z for 2 GS-35b will be about 850-900 Ohms at 3KV 2A.
> You can?t drive the tube to an anode voltage of 0V, so you may only use 
> the
> voltage swing for your calculation.
> The mode will be AB2 and that means a K of 1.6.
> As Thomas mentioned you will need capacitors with very low C min, so 
> better
> use small capacitors and add padders for the lower band.
> For optimum Q and shortest leads to the band switch you will need 3 or 4
> coils.
> The arrangement of tank components is quite critical, construct for 
> shortest
> possible lead length.
> 3 tube amps with 3xGS31 and 3xQB5/1750 have been built successfully with
> almost same power and efficiency on all bands.
> Probably you will need to use vacuum variables for small Cmin and high
> circulating currents anyway, so you will be better off to mount them
> vertically, which gives you less stray capacity.
>
> 73
> Peter
>
>> By means of those values I arrive by a load resistance of  693 ohm.(Ra=
>> Ua/Ia*K=1.87) like the formula tells
>
>> Some guys told my that it is not possible to obtain a good tuning with
>> such low load resistance,in this case you have to use other LOAD filter
>> configurations instead of a simple classical PI-filter !!
>
> No, that is no problem with a pi circuit
>
>
>
>> - Some bands is it not possible to tune(21Mhz and higher not possible and
>> no L-coil anymore in circuit).
>> - I  most of the time are both capacitors C1 and C2 totally turned open
>
> There is something totally bad, it might be difficult on the higher
> frequencies of 10m but not already at 15m.
>
>
>
>
> ------------------------------
>
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> End of Amps Digest, Vol 82, Issue 34
> ************************************ 