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11th Feb 2020, 12:16 pm | #1 |
Pentode
Join Date: Jul 2007
Location: Salisbury, Wiltshire, UK.
Posts: 174
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Shortwave frequency for pantry TX
This a FM/ MW pantry transmitter that I made several years ago which is in constant use. I going to design another one that will be a bit more sophisticated with VU meters etc., I want to make it 3 band to include shortwave, The big question what part of the shortwave band that is relatively quiet.
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11th Feb 2020, 12:22 pm | #2 |
Heptode
Join Date: Apr 2009
Location: Scratby, Norfolk, UK.
Posts: 648
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Re: Shortwave frequency for pantry TX
Hi,
As we are now in a sunspot minimum I would suggest anything above 15MHz would be pretty quiet. Kind regards Dave |
11th Feb 2020, 7:09 pm | #3 |
Guest
Posts: n/a
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Re: Shortwave frequency for pantry TX
Corr that's a good idea, most vintage sets have a (usually unused) shortwave band. I spent a while finding a blank spot on MW for my pantry job. Lots of gaps in SW, just have a tune around, and nobody is likely to receive your transmission either. And the aerial is more efficient, all green and saving energy, win win as it is said.
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11th Feb 2020, 7:33 pm | #4 |
Dekatron
Join Date: Apr 2012
Location: Wiltshire, UK.
Posts: 13,951
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Re: Shortwave frequency for pantry TX
Mine is in the 49-Metre band.
My thought-logic being that there are still quite a few broadcasters running many Kilowatts in that band so my few tens of milliwatts are likely to go unnoticed. "Hiding in plain sight" as they say. Also, I happened to have an ex-WWII US Army surplus FT243 crystal for what turned out to be an unused 5KHz in that range. |
11th Feb 2020, 10:58 pm | #5 |
Nonode
Join Date: May 2007
Location: Redruth, Cornwall, UK.
Posts: 2,562
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Re: Shortwave frequency for pantry TX
Hi.
That's sounds a great idea to operate a pantry transmitter in the SW band. I look forward to seeing your completed circuit. Would you mind sharing the circuit details of your FM/MW pantry transmitter in the pic which looks very neet indeed? Regards, Symon. |
11th Feb 2020, 11:41 pm | #6 |
Moderator
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,800
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Re: Shortwave frequency for pantry TX
Go the whole hog and have station announcements in Gobbledygook or Elbonian, featuring highly optimistic tractor production figures, and have a musical box station ID. "And a printed copy of the president's collected thoughts is available on request from the charge d'affaires, the Elbonian embassy, London or Paris."
David
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Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done |
11th Feb 2020, 11:43 pm | #7 |
Octode
Join Date: Jun 2013
Location: Fleet, Hampshire, UK
Posts: 1,764
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Re: Shortwave frequency for pantry TX
I was wondering about this myself recently, as stated, short antennas are far more efficient in the short wave band. On medium wave, 100mw or less into a piddly little wire antenna requires witch craft to reliably cover a whole property and get beyond the noise, and even then you may be out of luck!
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12th Feb 2020, 12:07 am | #8 |
Nonode
Join Date: Oct 2010
Location: Tintinara, South Australia, Australia
Posts: 2,324
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Re: Shortwave frequency for pantry TX
Before anybody goes putting pantry transmitters on the SW bands, I would suggest you find/get a detailed frequency use listing for the UK.
There are Defense and Emergency Service frequencies spread out on some strange frequencies you definitely don't want to be interfering with (even with short range gear). Also be aware SW is more actively monitored than MW frequencies, by various agencies. As an example of what is happening on SW :- https://www.dvidshub.net/news/362206...ry-warfighting |
12th Feb 2020, 12:43 am | #9 |
Dekatron
Join Date: May 2006
Location: Invercargill, New Zealand
Posts: 3,440
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Re: Shortwave frequency for pantry TX
Good point, out of curiosity I had a look at 49m band licenses in NZ, and found someone who may get a little upset in the middle of the various RNZI allocations...
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12th Feb 2020, 5:51 am | #10 |
Moderator
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,800
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Re: Shortwave frequency for pantry TX
100mW into a reasonable antenna, when a band is open, has been known to cross the Atlantic. There is an active intruder watch organisation monitoring amateur bands. Anything unusual noticed on the aviation HF frequencies gets reported and results in police action with transgressors accused of putting air passengers' lives at risk. What gives very short range coverage now in a sunspot minimum will be very different in a few year's time.
Medium wave listeners tend to tune to stations they know. Shortwave listeners tend to trawl around searching for anything interesting. You only have to look up 'The Buzzer' and 'The Squeaky Wheel' to see how much interest the unexplained generates. David
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Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done |
12th Feb 2020, 10:40 am | #11 | |
Nonode
Join Date: Apr 2012
Location: Worcestershire, UK.
Posts: 2,039
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Re: Shortwave frequency for pantry TX
[QUOTE=Radio Wrangler;1216476]
Quote:
Brilliant ... that's made my morning. I find myself wondering whether the pirate brig 'Justdontgetcaught' is about to scrape paint from the bows of the good ship 'Forumrules' ... Guy Last edited by Nymrod121; 12th Feb 2020 at 10:48 am. Reason: afterthought prompted by R-W's comment re HF distress freqs etc |
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12th Feb 2020, 1:04 pm | #12 |
Dekatron
Join Date: Aug 2007
Location: W.Butterwick, near Doncaster UK.
Posts: 8,923
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Re: Shortwave frequency for pantry TX
No comment!No pun intended but we need to stay under the radar.
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G8JET BVWS Archivist and Member V.M.A.R.S |
12th Feb 2020, 1:59 pm | #13 |
Moderator
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,800
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Re: Shortwave frequency for pantry TX
Indeed. The short wave bands would be a bad place to put a pantry transmitter. Only radios with the right frequency coverage could benefit from it, while medium wave is a lot more universal.
A shortwave pantry transmitter is a bit of a laugh as a concept. But I'd discourage anyone from doing it. David
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Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done |
12th Feb 2020, 4:03 pm | #14 |
Pentode
Join Date: Jul 2007
Location: Salisbury, Wiltshire, UK.
Posts: 174
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Re: Shortwave frequency for pantry TX
Thanks everyone for there input on this thread.
maybe I will give the shortwave a miss. I will probably come with a different approach, make it FM/MW and then be able switch it to two FM transmitters on two different frequencies and feed one with right hand audio and the other with left audio so that I can have two Radios going together to give me stereo. |
12th Feb 2020, 4:25 pm | #15 |
Dekatron
Join Date: Feb 2003
Location: Cottingham, East Yorkshire, UK.
Posts: 5,737
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Re: Shortwave frequency for pantry TX
I don't really understand what the rationale of using SW in preference to MW is. At first sight, when looking at the UK MW band-plan it looks like there are wall to wall stations, but many are very local using only 1 Watt. If using a pantry transmitted with a valve radio that doesn't have a built in frame aerial or ferrite rod, with no external aerial plugged in only the pantry transmitter will occupy the band. If the set does have a frame aerial/ferrite rod, there should be plenty of empty slots and if there is a nearby interfering station, rotating the set should null that out.
This last two or three years, I've made well over 20 'Guy Fernando'/BVWS Bulletin FM/AM converters and several Mini Mods and never had a problem. That said, the last thing I'd want to do is to discourage anyone from experimenting and homebrewing, and the TX in the first post in this thread looks very nicely constructed, so every good wish to the OP in his endeavours. The list of MW UK transmitters, their location and power levels can be found here: http://www.mediumwaveradio.com/uk.php
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David. BVWS Member. G-QRP Club member 1339. |
12th Feb 2020, 7:14 pm | #16 | |
Heptode
Join Date: Dec 2014
Location: Lincoln, Lincolnshire, UK.
Posts: 583
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Re: Shortwave frequency for pantry TX
Quote:
I think some of the other BBC MW stations no longer exist either. |
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12th Feb 2020, 7:52 pm | #17 | |
Dekatron
Join Date: Feb 2007
Location: Lynton, N. Devon, UK.
Posts: 7,060
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Re: Shortwave frequency for pantry TX
Quote:
MW is a broadcast band... if there's no reception on a particular frequency in the morning, nothing in the evening, and nothing in the night, then consider that you could have your little pantry transmitter running locally for your pleasure, at that frequency with nobody the wiser. SW has lots of uses... Some broadcast transmissions, but some emergency, defence, shipping etc which may start transmitting at any time, expecting the frequency to be clear. And receiving stations could be monitoring all the time, ready for an unplanned transmission. The last think you want to happen is for your little pantry jobbie to be heard, radiating efficiently from a wire aerial, possibly jeopardising an important 'proper' transmission. Using SW does sound attractive, why not use that unused switch position on so many 1940's and 1950's woodies? But, extreme caution is definitely the watchword. |
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12th Feb 2020, 8:05 pm | #18 |
Octode
Join Date: Jun 2013
Location: Fleet, Hampshire, UK
Posts: 1,764
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Re: Shortwave frequency for pantry TX
The problem with MW transmitters is if you live in a house where the construction and/or electrical wiring impedes your signal getting through, then all of the micro power 100mw jobs are pretty useless if you want full coverage. So it’s either a case of lashing up a huge antenna wire indoors and possibly your own ATU or looking for more power. Neither of which are easy. You can’t buy anything higher powered and discussion of getting more power from an existing TX usually gets shot down down with talk of propagation etc, which is never going to happen from a 2-3 meter wire. All this is fine if you make your own or modify one yourself with a linear PA as I’ve been looking at.
This doesn’t mean shortwave is a good idea, the comments here seem to sound like it really isn’t. But I can see the appeal in being able to deliver better power transfer to an antenna. Much talk is made about pantry transmitters in the AM band and limiting power, but with medium wave frequencies, very little power will end up in a short antenna and you then have to compete with all the noise around today. All of that said, I have learned a lot from my various endeavours to create localised AM radio in my home, so perhaps I’m lucky it’s been such a challenge for me!! |
12th Feb 2020, 8:41 pm | #19 |
Heptode
Join Date: Jan 2009
Location: West Lothian, UK.
Posts: 760
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Re: Shortwave frequency for pantry TX
Some vintage radios used to have a link to use the mains wiring as an aerial.
How about doing the reverse and using your house wiring as the local radiator - joining all the wifi extenders...
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George |
12th Feb 2020, 8:44 pm | #20 |
Octode
Join Date: Jun 2013
Location: Fleet, Hampshire, UK
Posts: 1,764
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Re: Shortwave frequency for pantry TX
Ah yes, I’ve considered looking at carrier current and may do at some point. I’d imagine mains hum would be present on the signal though, but would be interesting to try
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