Hi All,
I see quite a few members of this group asking about exciters, amps, antennas
etc, so here goes:-
I'm active on 630m, usually WSPR but also JT9 and FT8. I had been active on
136khz and I am basically using the same set up with a few mods for the 630m
band. Virtually everthing was built from my junk box.
Exciter - FT1000MP MK V Field transmitting on 10MHz with TX power as minium.
Receiving directly on 630m.
Transverter - output of the FT1000MP feeds an attenuator to further drop the
power to a suitable level (<1mW) to feed into a Mini-Circuits SBL-1 DBM. Local
oscillator is a cheap packaged 10MHz TCXO available from most component houses
(seehttp://uk.rs-online.com/web/p/crystal-oscillators/1442367/ but with through
hole pins as opposed to surface mount) Two further stages using push-pull
Mosfets get the power up to about 4 watts. The transverter is linear .
Amplifier - A full bridge Mosfet amplifer running in Class D using 4 IRFP640
devices with a HT of 225V. The output of the transverter feeds a transformer
wound on a small ferrite toroid core having 4 winding each feeding on of the
Mosfet gates. The amplifier output is a large EPCOS ferrite toroid (
http://uk.rs-online.com/web/p/ferrite-rings/2120718/ ) with the output winding
tapped for different power levels. The amp will produce well over 1kW and
barely gets warm and is quite happy at my normal power level of 300watts
running WSPR with its 2 minute transmit cycle. The amp includes clamp diodes
etc as a form of protection.
Low Pass Filter - a nine element LPF to remove the rubbish from the class D
amp!
Antenna - Top loaded vertical - vertical section approx 7 metres with a further
15 metres horizontal wire for top loading but the top loading section is
doubled back on itself to fit in a suburban garden. The antenna is tuned with
bottom loaded coil approx 300 mm diameter with variometer (homebrewed) for
tuning. Radial system buried in lawn.
Does it work? - I'm running the system now - go to
http://wsprnet.org/drupal/wsprnet/map select MF and a Time Period of, say, 12
hours and see who I received and who received me! You'll find me to the west of
London near G4CAO. One of the problems with 630m is that there are many people
listening but not many transmitting so please get the soldering iron out and
start building!
David G4FTC
________________________________
From: Amps <amps-bounces@contesting.com> on behalf of Chris Wilson
<chris@chriswilson.tv>
Sent: 10 November 2017 21:31
To: amps@contesting.com
Subject: Re: [Amps] Amplifier for 630 meter band
Hello Catherine,
I run several W1VD design Class D MOSFET amps on LF (136kHz) and they
perform really well. Most expensive item to source here in the UK is
the LPF toroids, mainly di=ue to carriage from the USA. Heatsink
requirements are extremely modest, and an HP 50V server SMPS runs one
a treat, and those too are dirt cheap used, over in the US. I get into
East coast nUSA on LF using WSPR and we are only allowed 1W ERP...
I too fancy making a GS35B tube LF amp, but sourcing the caps would be
a costly PITA over here I feel.I do have the HV and filament supplies
for one though, should I feel like having a go at one. Good luck!
2E0ILY
Here's the link to his designs:
http://www.w1vd.com/137-500-KWTX.html
A 137 & 500 kHz Class-D Kilowatt RF Deck -
W1VD<http://www.w1vd.com/137-500-KWTX.html>
www.w1vd.com
A 137 & 500 kHz Class-D Kilowatt RF Deck. This 137 & 500 kHz Class-D Kilowatt
rf deck was built for use at WD2XNS (136 - 138 kHz) and WE2XGR/2 (465 - 515
kHz) to ...
On Friday, November 10, 2017, you wrote:
> "U may well have a tough time stuffing parts into a SB-200
> chassis. This is where a simple, bigger box would help out.
> Something like a single 3-400Z / 3-500Z would do the trick, dead
> simple. Then u could also stuff a 4-400 A / B /C in there as well."
> Yes, it may make sense to pull some of the larger tuning and LP
> filtering components into a separate case, outside the SB-200 case.
> One nice thing about VLF is that tolerances are very loose for
> things like lead lengths. Just be sure that wires carrying high voltages are
> very well insulated.
> I'm certainly open to having a second case with the additional
> filtering components. That second case won't have a power supply or
> tubes needing cooling, which simplifies things greatly.
> I'm not dead set on starting with an SB-200 by any means. If a junk
> 3-500Z or 4-400 amp drops into my lap, I could just as readily run
> with that. I will check out NEARFEST on the spring and see what turns up.
> If anyone in New England reads this and thinks they may have a
> suitable amp for sale (no tubes is fine, burned bandswitch is fine,
> power supply must be good, price must reflect condition; looking for
> a low-priced junker amp for extensive modifications), please reach out to me
> directly.
> 73,
> Cathy
> N5WVR
> <n5wvr@arrl.net>
> _______________________________________________
> Amps mailing list
> Amps@contesting.com
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Best regards,
Chris mailto:chris@chriswilson.tv
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