AM pantry transmitter design by someone 'out there' - UK Vintage Radio Repair and Restoration Discussion Forum

kalee20 · 18th Nov 2011, 2:42 pm

See here.

There's a link to the person's own site, with fuller information.

I do like the honeycomb coil!

Robert Darwent · 18th Nov 2011, 3:36 pm

Thanks for that most interesting link. I did a bit of searching and found that the author in question is Manfred Mornhinweg, XQ2FOD and he has quite a few webpages devoted to his vintage radio restorations too, well worth a look.

http://ludens.cl/Radiohis/radiohis.html

http://www.qsl.net/xq2fod/

Regards

murphyv310 · 19th Nov 2011, 1:16 am

I wonder if it is as clean as my EH90 pantry job?

fetteler · 19th Nov 2011, 1:38 am

This is very interesting. Excuse my ignorance of the term "pantry transmitter" but am I mistaken in assuming it refers to a transmitter which has a notional range limited to an area approximating that of a pantry, whatever the area of a pantry is?!

Cheers,
Steve.

HamishBoxer · 19th Nov 2011, 7:28 pm

Correct! or near enough.

David GM8JET

PS It's not meant for all the street to pickup. In your house only, or for your ears only.

fetteler · 20th Nov 2011, 5:55 pm

Thanks Hamish - I think I'll put this project on my (already bloated!) to do list

Cheers
Steve.

HamishBoxer · 20th Nov 2011, 9:13 pm

PS Trevors design i think will be very clean.

greenstar · 26th Nov 2011, 11:29 pm

Can't find Trevor's job - looked at his posts - Trevor, where is it?
Tony

FRANK.C · 27th Nov 2011, 12:08 am

Hi Tony
I think you will find Trevor's design here and here.

Frank

val33vo · 30th Nov 2011, 7:47 pm

I dont want to be unenterprising but just remind all this circuit is illegal in the UK and you can never be sure how far it will radiate

val33vo

kalee20 · 30th Nov 2011, 8:47 pm

All true.

Responsible use dictates that you go walkabout with a portable receiver to check that you don't transmit beyond your property boundaries.

And that includes on harmonics, too - you might have to modify your receiver to check between MW and SW, unless you have a continuous coverage receiver. A few feet of wire is much more efficient at higher frequencies, so unless you have very low harmonics, you could be radiating, unknowingly, much farther than you think!

murphyv310 · 30th Nov 2011, 9:42 pm

Quote:

Originally Posted by val33vo

I dont want to be unenterprising but just remind all this circuit is illegal in the UK and you can never be sure how far it will radiate

Hi.
Any MW transmitter is illegal in the UK whether 10mw or 100w. My circuit was built for quality not power which was explained in the thread. The 6L6 was driven by a very low drive and was purely a buffer.
I now use my design and an AMT3000. As I have pointed out even 10mw is illegal and you do this at your own risk!

Quote:

Originally Posted by kalee20

And that includes on harmonics, too !

Hi.
Very wise words, the AMT3000 is a very well designed unit and with its switch-able Pi tuning and gives a very clean signal.
My own little TX has now been migrated to PCB and has an EF91 as the "PA" and also has a proper PI Tank set up, it works as well as the AMT and the use of an audio matching TX now has stopped some annoying hum due to loops completely.

petervk2mlg · 11th Jul 2014, 12:13 am

Is Chas Miller's Radiophile transmitter circuit avaliable anywhere online?
P

Phil G4SPZ · 11th Jul 2014, 7:31 am

Peter,

Send me a PM with your e-mail address and I'll scan the original Radiophile article for you.

You'll need to obtain a 12SA7 valve and a Wearite PHF2 coil to build it.

Phil G4SPZ · 14th Jul 2014, 10:51 pm

Peter,

Details now sent by direct e-mail. Sorry for the delay.

73 de Phil

paulsherwin · 15th Jul 2014, 12:37 am

Peter, pantry transmitter designs are basically oscillators, sometimes with a PA stage. Valve designs aren't very fussy and you can usually use whatever you have to hand - for example, if the design uses a triode and you only have a pentode, then just triode wire it.

The main drawback with any valve microtransmitter design is the power requirement, given that only a few mW of ERP are going to be produced. They do tend to be simpler than solid state designs though.

petervk2mlg · 15th Jul 2014, 1:10 am

Ok, Paul thanks.
I have built a couple of MATE transmitters and they work well enough.
After reading some Radiophiles I thought I'd like to have a go at Chas's project.
Now I have the original article from Radiophile, thanks to Phil. Getting the right coil might be a challenge, although I do have an RF coil from Antique Electronic Supply in USA. That might work.

Phil G4SPZ · 18th Jul 2014, 5:22 pm

The coil is in the post, Peter

petervk2mlg · 29th Jul 2014, 1:04 am

Apologies if this is a silly question, but what is the difference between an oscillator coil and an RF coil such as the Wearite PHF2?
When planning to build this pantry transmitter I had initially thought of using an oscillator coil I had from AES in USA.
Phil kindly supplied me with the nominated coil in Chas's design - the PHF2.
This got me puzzling about the differences between an oscillator coil and an RF coil.

TIA

Peter

kalee20 · 29th Jul 2014, 10:37 am

Inductances will be different - the oscillator coil will generally need to tune about 460kHz higher in frequency. So you'll need a different capacitor value to tune in-band.

The turns ratio may also be different for the aerial coupling coil for aerial coupling, and the feedback coil for the oscillator. But circuit tweaking will probably allow one to be used in place of the other here.

18th Nov 2011, 2:42 pm	#1
kalee20 Dekatron Join Date: Feb 2007 Location: Lynton, N. Devon, UK. Posts: 7,088	AM pantry transmitter design by someone 'out there' See here. There's a link to the person's own site, with fuller information. I do like the honeycomb coil!

18th Nov 2011, 3:36 pm	#2
Robert Darwent Heptode Join Date: Aug 2006 Location: Sheffield, South Yorkshire, UK Posts: 990	Re: AM pantry transmitter design by someone 'out there' Thanks for that most interesting link. I did a bit of searching and found that the author in question is Manfred Mornhinweg, XQ2FOD and he has quite a few webpages devoted to his vintage radio restorations too, well worth a look. http://ludens.cl/Radiohis/radiohis.html http://www.qsl.net/xq2fod/ Regards __________________ Robert G0UHF www.wavesintheair.co.uk

19th Nov 2011, 1:16 am	#3
murphyv310 Dekatron Join Date: Sep 2006 Location: Kilmarnock, Ayrshire, UK. Posts: 5,422	Re: AM pantry transmitter design by someone 'out there' I wonder if it is as clean as my EH90 pantry job? __________________ Cheers, Trevor. MM0KJJ. RSGB, GQRP, WACRAL, K&LARC. Member

19th Nov 2011, 1:38 am	#4
fetteler Octode Join Date: Jul 2011 Location: Staffordshire Moorlands, UK. Posts: 1,479	Re: AM pantry transmitter design by someone 'out there' This is very interesting. Excuse my ignorance of the term "pantry transmitter" but am I mistaken in assuming it refers to a transmitter which has a notional range limited to an area approximating that of a pantry, whatever the area of a pantry is?! Cheers, Steve. __________________ Those who lack imagination cannot imagine what is lacking...

19th Nov 2011, 7:28 pm	#5
HamishBoxer Dekatron Join Date: Aug 2007 Location: W.Butterwick, near Doncaster UK. Posts: 8,935	Re: AM pantry transmitter design by someone 'out there' Correct! or near enough. David GM8JET PS It's not meant for all the street to pickup. In your house only, or for your ears only.

20th Nov 2011, 5:55 pm	#6
fetteler Octode Join Date: Jul 2011 Location: Staffordshire Moorlands, UK. Posts: 1,479	Re: AM pantry transmitter design by someone 'out there' Thanks Hamish - I think I'll put this project on my (already bloated!) to do list Cheers Steve. __________________ Those who lack imagination cannot imagine what is lacking...

20th Nov 2011, 9:13 pm	#7
HamishBoxer Dekatron Join Date: Aug 2007 Location: W.Butterwick, near Doncaster UK. Posts: 8,935	Re: AM pantry transmitter design by someone 'out there' PS Trevors design i think will be very clean.

26th Nov 2011, 11:29 pm	#8
greenstar Octode Join Date: Jul 2011 Location: Leicester, Leics. UK. Posts: 1,685	Re: AM pantry transmitter design by someone 'out there' Can't find Trevor's job - looked at his posts - Trevor, where is it? Tony

27th Nov 2011, 12:08 am	#9
FRANK.C Heptode Join Date: Feb 2006 Location: Roscommon, Ireland Posts: 732	Re: AM pantry transmitter design by someone 'out there' Hi Tony I think you will find Trevor's design here and here. Frank

30th Nov 2011, 7:47 pm	#10
val33vo Retired Dormant Member Join Date: Apr 2008 Location: Banffshire, Scotland, UK. Posts: 191	Re: AM pantry transmitter design by someone 'out there' I dont want to be unenterprising but just remind all this circuit is illegal in the UK and you can never be sure how far it will radiate val33vo

30th Nov 2011, 8:47 pm	#11
kalee20 Dekatron Join Date: Feb 2007 Location: Lynton, N. Devon, UK. Posts: 7,088	Re: AM pantry transmitter design by someone 'out there' All true. Responsible use dictates that you go walkabout with a portable receiver to check that you don't transmit beyond your property boundaries. And that includes on harmonics, too - you might have to modify your receiver to check between MW and SW, unless you have a continuous coverage receiver. A few feet of wire is much more efficient at higher frequencies, so unless you have very low harmonics, you could be radiating, unknowingly, much farther than you think!

11th Jul 2014, 12:13 am	#13
petervk2mlg Heptode Join Date: Jan 2007 Location: Parkes, NSW Australia Posts: 877	Re: AM pantry transmitter design by someone 'out there' Is Chas Miller's Radiophile transmitter circuit avaliable anywhere online? P

11th Jul 2014, 7:31 am	#14
Phil G4SPZ Dekatron Join Date: Apr 2005 Location: Bewdley, Worcestershire, UK. Posts: 4,748	Re: AM pantry transmitter design by someone 'out there' Peter, Send me a PM with your e-mail address and I'll scan the original Radiophile article for you. You'll need to obtain a 12SA7 valve and a Wearite PHF2 coil to build it. __________________ Phil Optimist [n]: One who is not in possession of the full facts

14th Jul 2014, 10:51 pm	#15
Phil G4SPZ Dekatron Join Date: Apr 2005 Location: Bewdley, Worcestershire, UK. Posts: 4,748	Re: AM pantry transmitter design by someone 'out there' Peter, Details now sent by direct e-mail. Sorry for the delay. 73 de Phil __________________ Phil Optimist [n]: One who is not in possession of the full facts

15th Jul 2014, 12:37 am	#16
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,971	Re: AM pantry transmitter design by someone 'out there' Peter, pantry transmitter designs are basically oscillators, sometimes with a PA stage. Valve designs aren't very fussy and you can usually use whatever you have to hand - for example, if the design uses a triode and you only have a pentode, then just triode wire it. The main drawback with any valve microtransmitter design is the power requirement, given that only a few mW of ERP are going to be produced. They do tend to be simpler than solid state designs though.

15th Jul 2014, 1:10 am	#17
petervk2mlg Heptode Join Date: Jan 2007 Location: Parkes, NSW Australia Posts: 877	Re: AM pantry transmitter design by someone 'out there' Ok, Paul thanks. I have built a couple of MATE transmitters and they work well enough. After reading some Radiophiles I thought I'd like to have a go at Chas's project. Now I have the original article from Radiophile, thanks to Phil. Getting the right coil might be a challenge, although I do have an RF coil from Antique Electronic Supply in USA. That might work.

18th Jul 2014, 5:22 pm	#18
Phil G4SPZ Dekatron Join Date: Apr 2005 Location: Bewdley, Worcestershire, UK. Posts: 4,748	Re: AM pantry transmitter design by someone 'out there' The coil is in the post, Peter __________________ Phil Optimist [n]: One who is not in possession of the full facts

29th Jul 2014, 1:04 am	#19
petervk2mlg Heptode Join Date: Jan 2007 Location: Parkes, NSW Australia Posts: 877	Re: AM pantry transmitter design by someone 'out there' Apologies if this is a silly question, but what is the difference between an oscillator coil and an RF coil such as the Wearite PHF2? When planning to build this pantry transmitter I had initially thought of using an oscillator coil I had from AES in USA. Phil kindly supplied me with the nominated coil in Chas's design - the PHF2. This got me puzzling about the differences between an oscillator coil and an RF coil. TIA Peter

29th Jul 2014, 10:37 am	#20
kalee20 Dekatron Join Date: Feb 2007 Location: Lynton, N. Devon, UK. Posts: 7,088	Re: AM pantry transmitter design by someone 'out there' Inductances will be different - the oscillator coil will generally need to tune about 460kHz higher in frequency. So you'll need a different capacitor value to tune in-band. The turns ratio may also be different for the aerial coupling coil for aerial coupling, and the feedback coil for the oscillator. But circuit tweaking will probably allow one to be used in place of the other here.