[600MRG] 600MRG Digest, Vol 1, Issue 32

Sun Jan 28 19:55:14 EST 2018

 Eric wrote:

If going to parallel 807s (or 1625s), a 6AG7 oscillator (xtal or ECO) 
probably won't have enough output to fully excite the pair.

I think it can, if operating on the fundamental.  My "Secret Dream" transmitter made 100 watts output with a 6AG7 driving a pair of 807s.   Power supply was a Heath HP-23.

http://www.wd8das.net/dream.html

Steve WD8DAS

sbjohnston at aol.com
http://www.wd8das.net/
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Subject: 600MRG Digest, Vol 1, Issue 32

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Today's Topics:

   1. 630 meter Homebrew (Dwight Blevins)
   2. Re: 630 meter Homebrew (Eric NO3M)
   3. Re: 630 meter Homebrew (Edward R Cole)
   4. Tuning inductor design (Rudy Severns)

----------------------------------------------------------------------

Message: 1
Date: Sun, 28 Jan 2018 21:37:32 +0000 (UTC)
From: Dwight Blevins <blethn at yahoo.com>
To: "600mrg at mailman.qth.net" <600mrg at mailman.qth.net>
Subject: [600MRG] 630 meter Homebrew
Message-ID: <946878017.2218828.1517175452481 at mail.yahoo.com>
Content-Type: text/plain; charset="utf-8"

I see there's an ongoing discussion on a homebrew tube transmitter for 630 meters. I just built one and it was a most rewarding experience. It was a bit more difficult than I expected, but quite doable for the average ham. Mine is a takeoff on one posted online by a ham in Australia (VK1S?). He used a 6AG7 to drive an 807. I used a 1625 for the final, much the same tube as the 6BG6, 807, 1625, 6l6, etc. It produces about 20 watts output.
Forget the ease of the old 6V6/6L6 style transmitters, which most all of us have tried at some point in the hobby. The high value L/C configurations of the MF/LF spectrum are something located in the pages of another book that many of us have not yet read. Thankfully the online schematic that I found got me in the ballpark, but I still spent several days of cut and try, getting things to gel for my particular setup. I learned some valuable lessons that I'll not soon forget. 

If I had it to do over (and I probably will) I'd have gone for a dual, parallel output in the final. This would produce around 35 to 40 watts out, which, based on my experience thus far, I feel is minimal and needful from a practical standpoint. Many of us do not have a very efficient antenna, so I feel that if you don't have at least something close to a minimum power in the 40 to 50 watt range, then you'll have considerable difficulty making contacts with cw. The challenge might be a little less for those living in areas of high population, but there are just not yet that many hams operating 630m. 

Living in the high desert of western Colorado, it can be a pretty good challenge trying to work another ham beyond the high Rockies to the east, and the Sierra Nevada to the west. Going north and south there are probably at least 100,000 Jackrabbits between me and the next closest 630m antenna. A couple of hams have copied my signal, including KB5NJD, but I have yet to validate a single two-way QSO. 
Am I discouraged? Of course, not. The challenge just enhances the joy of it all! 

To me, 630m is a homebrew tinker's paradise. Right now that's what thrills me the most, so this is where I'll be; pounding the brass and looking for that one and first elusive response to my CQ, which I know lies somewhere on the future horizon. 

Ike, KW7T

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Message: 2
Date: Sun, 28 Jan 2018 17:12:34 -0500
From: Eric NO3M <no3m at no3m.net>
To: 600mrg at mailman.qth.net
Subject: Re: [600MRG] 630 meter Homebrew
Message-ID: <19aed4f5-8174-e632-9bdf-76933dc3964c at no3m.net>
Content-Type: text/plain; charset="utf-8"; Format="flowed"

I recently built an amplifier that uses a similar lineup: 6AG7 -> 6V6 -> 
2x 807 (parallel).? 1mW or less is plenty of drive.? It could be 
converted to a stand-alone rig by modifying the first driver stage as an 
ECO.

If going to parallel 807s (or 1625s), a 6AG7 oscillator (xtal or ECO) 
probably won't have enough output to fully excite the pair. Following 
the 6AG7 with a 6V6, 6F6, or 6L6 running Class A (untuned grid, tuned 
plate) will do the job as well as provide excellent buffering.? If using 
an ECO, the grid may have to be tuned to 1/2 freq. for best stability; 
at least that's the best configuration in my 89 -> 42 -> 802 exciter, 
even on 630M.

If you want to graduate to the next power level from 2x 807s and like 
the old beam tubes, try a pair of 814s.? Need more, a single or pair of 
813s.

It's nice to hear about some of the glowbugs floating around on 630M.

73 Eric NO3M

On 01/28/2018 04:37 PM, Dwight Blevins via 600MRG wrote:
> I see there's an ongoing discussion on a homebrew tube transmitter for 
> 630 meters. I just built one and it was a most rewarding experience. 
> It was a bit more difficult than I expected, but quite doable for the 
> average ham. Mine is a takeoff on one posted online by a ham in 
> Australia (VK1S?). He used a 6AG7 to drive an 807. I used a 1625 for 
> the final, much the same tube as the 6BG6, 807, 1625, 6l6, etc. It 
> produces about 20 watts output.
>
> Forget the ease of the old 6V6/6L6 style transmitters, which most all 
> of us have tried at some point in the hobby. The high value L/C 
> configurations of the MF/LF spectrum are something located in the 
> pages of another book that many of us have not yet read. Thankfully 
> the online schematic that I found got me in the ballpark, but I still 
> spent several days of cut and try, getting things to gel for my 
> particular setup. I learned some valuable lessons that I'll not soon 
> forget.
>
> If I had it to do over (and I probably will) I'd have gone for a dual, 
> parallel output in the final. This would produce around 35 to 40 watts 
> out, which, based on my experience thus far, I feel is minimal and 
> needful from a practical standpoint. Many of us do not have a very 
> efficient antenna, so I feel that if you don't have at least something 
> close to a minimum power in the 40 to 50 watt range, then you'll have 
> considerable difficulty making contacts with cw. The challenge might 
> be a little less for those living in areas of high population, but 
> there are just not yet that many hams operating 630m.
>

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Message: 3
Date: Sun, 28 Jan 2018 13:34:29 -0900
From: Edward R Cole <kl7uw at acsalaska.net>
To: Dwight Blevins <blethn at yahoo.com>,	"600mrg at mailman.qth.net"
	<600mrg at mailman.qth.net>
Subject: Re: [600MRG] 630 meter Homebrew
Message-ID: <201801282234.w0SMYWNm015974 at mail42c28.carrierzone.com>
Content-Type: text/plain; charset="us-ascii"; format=flowed

Only 20w?  I had an old DX-100 that used two 1625's in the plate 
modulator and produced 120w at audio.  500-KHz is not that much 
higher in freq.  Two 6146 will do 150w at HF and 110w at 6m (what was 
in my SB-110).  Of course this was class-B in the modulator and class-C at RF.

73, Ed

At 12:37 PM 1/28/2018, Dwight Blevins via 600MRG wrote:
>I see there's an ongoing discussion on a homebrew tube transmitter 
>for 630 meters. I just built one and it was a most rewarding 
>experience. It was a bit more difficult than I expected, but quite 
>doable for the average ham. Mine is a takeoff on one posted online 
>by a ham in Australia (VK1S?). He used a 6AG7 to drive an 807. I 
>used a 1625 for the final, much the same tube as the 6BG6, 807, 
>1625, 6l6, etc. It produces about 20 watts output.
>
>Forget the ease of the old 6V6/6L6 style transmitters, which most 
>all of us have tried at some point in the hobby. The high value L/C 
>configurations of the MF/LF spectrum are something located in the 
>pages of another book that many of us have not yet read. Thankfully 
>the online schematic that I found got me in the ballpark, but I 
>still spent several days of cut and try, getting things to gel for 
>my particular setup. I learned some valuable lessons that I'll not 
>soon forget.
>
>If I had it to do over (and I probably will) I'd have gone for a 
>dual, parallel output in the final. This would produce around 35 to 
>40 watts out, which, based on my experience thus far, I feel is 
>minimal and needful from a practical standpoint. Many of us do not 
>have a very efficient antenna, so I feel that if you don't have at 
>least something close to a minimum power in the 40 to 50 watt range, 
>then you'll have considerable difficulty making contacts with cw. 
>The challenge might be a little less for those living in areas of 
>high population, but there are just not yet that many hams operating 630m.
>
>Living in the high desert of western Colorado, it can be a pretty 
>good challenge trying to work another ham beyond the high Rockies to 
>the east, and the Sierra Nevada to the west. Going north and south 
>there are probably at least 100,000 Jackrabbits between me and the 
>next closest 630m antenna. A couple of hams have copied my signal, 
>including KB5NJD, but I have yet to validate a single two-way QSO.
>Am I discouraged? Of course, not. The challenge just enhances the 
>joy of it all!
>
>To me, 630m is a homebrew tinker's paradise. Right now that's what 
>thrills me the most, so this is where I'll be; pounding the brass 
>and looking for that one and first elusive response to my CQ, which 
>I know lies somewhere on the future horizon.
>
>Ike, KW7T
>
>______________________________________________________________
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>
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73, Ed - KL7UW
   http://www.kl7uw.com
Dubus-NA Business mail:
   dubususa at gmail.com 

------------------------------

Message: 4
Date: Sun, 28 Jan 2018 15:01:50 -0800
From: "Rudy Severns" <n6lf at epud.net>
To: "600MRG" <600mrg at mailman.qth.net>
Subject: [600MRG] Tuning inductor design
Message-ID: <000001d3988b$fbb33c20$f319b460$@net>
Content-Type: text/plain; charset="us-ascii"

When I first posted my notes on LF-MF antenna design I had a chapter on
tuning inductor design.  While I don't think there were any major errors, I
was very unhappy with what I had written.  For that reason I yanked it off
my web page many months ago.  Since then I've completely rewritten it.  I
don't claim it's perfect but it should now be of some help to the LF-MF gang
so I've reposted Chapter 6, Tuning Inductor Design, on my web page:
www.antennasbyn6lf.com .

GL and 73, Rudy N6LF WD2XSH/20

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