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 Post subject: 10 meter coil info.
PostPosted: Jun Wed 13, 2018 3:47 pm 
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Joined: Sep Sat 06, 2008 6:17 pm
Posts: 975
Location: Central Pa, 17044
Hi all, Several years ago I built the Hart 25 CW transmitter.
It used a 5Y3 and a 6W6GT. and worked well on 40 and 80
meters.
My question is can I use this little 5 W output transmitter
on 10 meters?
I know I'll have to change to a 20mc. crystal,
What coils would I need to work 10 M
What I'm saying is, I need to know What wire size and
How many turns.
For 40 m. it's Plate is 31 turns of #20 wire close wound
Antenna coil 18 turns # 20 wire. I wound them on a pill
bottle. So what about 10M.

Thanks for any help,
Gary KB3WYZ


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 Post subject: Re: 10 meter coil info.
PostPosted: Jun Wed 13, 2018 7:20 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 33189
Location: Maryland 20709, USA
Gary T. Lane wrote:
My question is can I use this little 5 W output transmitter on 10 meters?
...
I know I'll have to change to a 20mc. crystal
Hi Gary,

You better change to a 28Mc crystal unless you want to operate on 15 meters.

Or 14Mc if the oscillator or buffer can be configured to work as a doubler.

- Leigh

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 Post subject: Re: 10 meter coil info.
PostPosted: Jun Wed 13, 2018 10:33 pm 
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Joined: Sep Sat 06, 2008 6:17 pm
Posts: 975
Location: Central Pa, 17044
Ok I meant 28mc..
Right now I have the 40&80 meter coils.
How many turns and what size wire and form diameter
should I use?

Gary :?


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 Post subject: Re: 10 meter coil info.
PostPosted: Jun Thu 14, 2018 2:56 am 
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Joined: Sep Sat 06, 2008 3:04 am
Posts: 203
Location: Benton City, WA
Leigh wrote:

You better change to a 28Mc crystal unless you want to operate on 15 meters.

Or 14Mc if the oscillator or buffer can be configured to work as a doubler.


Most rigs from that era multiplied to 20, 15, and 10 meters. So why would he need a 28mc/s crystal? You might even need to add a multiplier stage. Also I suspect that even if the rig doubled/tripled/quadrupled to 20, 15, or 10 meters I am not sure it would meet the spectral purity for current rigs.

Even then old rigs like the Eico 720 or DX-## could be easily tuned to the wrong harmonic of that crystal. Ask me how I know.

Thank you.
Jim


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 Post subject: Re: 10 meter coil info.
PostPosted: Jun Thu 14, 2018 3:03 am 
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Posts: 33189
Location: Maryland 20709, USA
Southerner wrote:
Leigh wrote:
You better change to a 28Mc crystal unless you want to operate on 15 meters.
Or 14Mc if the oscillator or buffer can be configured to work as a doubler.
Most rigs from that era multiplied to 20, 15, and 10 meters. So why would he need a 28mc/s crystal? You might even need to add a multiplier stage. Also I suspect that even if the rig doubled/tripled/quadrupled to 20, 15, or 10 meters I am not sure it would meet the spectral purity for current rigs.
Spectral purity is the main reason I suggested a 28Mc crystal in the first place.

I expect the 28Mc crystal would be a 3rd overtone, but still cleaner than multiplier output.

- Leigh

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http://www.AtwaterKent.info
Click "Grebe Stuff" for Synchrophase info


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 Post subject: Re: 10 meter coil info.
PostPosted: Jun Thu 14, 2018 3:17 am 
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Joined: May Tue 30, 2006 4:46 pm
Posts: 9383
Location: Santa Rosa, CA
6W6 was not designed as an RF amplifier, but it will work. Efficiency may not be good and you may get some strange oscillation at 28 Mhz.

I remember guys used to cut the bases off of 6L6 and 1625 to get better performance above 20 Mhz.

Rich


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 Post subject: Re: 10 meter coil info.
PostPosted: Jun Thu 14, 2018 3:22 am 
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Posts: 33189
Location: Maryland 20709, USA
Rich, W3HWJ wrote:
I remember guys used to cut the bases off of 6L6 and 1625 to get better performance above 20 Mhz.

Octal tubes as originally designed had just wire leads, with no base.

I guess going back to the original design was beneficial in this case.

- Leigh

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http://www.AtwaterKent.info
Click "Grebe Stuff" for Synchrophase info


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 Post subject: Re: 10 meter coil info.
PostPosted: Jun Fri 15, 2018 5:32 pm 
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Joined: Jan Fri 27, 2017 8:41 pm
Posts: 54
Location: Springwater, NY
Gary T. Lane wrote:
Ok I meant 28mc. Right now I have the 40&80 meter coils. How many turns and what size wire and form diameter should I use? Gary :?


Gary, check out this inductance calculator. I've found that it correlates nicely with measured results. Values will depend on your specific circuit and desire for the tuned element.

http://hamwaves.com/antennas/inductance.html

73, Dean, NW2K


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