Come on post your project please.... fieldstrength meter

Like B&Q for homebrew radios
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Taurus Flyer
Posts: 28
Joined: 06 Dec 2019, 11:56

Come on post your project please.... fieldstrength meter

Post by Taurus Flyer »

Still designing and make my radio's
Adjusting the maximum rf output of a transmitter better can be done bij measuring the field strength at some distance. It gives a better indication for the hand held transmitters.
Because I am also Ham operator I combined two instruments in one, in fact three instruments.
1. A sensitive monitor receiver to check for 'foreign'signals on the 27 MHz band.
2. A Dot bar indicator for fleid strength independent of frequency, use for my ham field tranceivers.
3. Bar dot display to show the 27 MHz carrier wave of the transmitter to tune. This bar dot display also shows the modulation depth of the tones that are send for each channel. With extracted antenne the signal can be measured at a distant of about 30 m, if retracted, also of the transmitter, for example 4/5 m. For tuning I use an entena length so the indication is 80 % at aroud 10 m. Of the last situation a short video, 50 % modulation depth.

Taurus Flyer
Posts: 28
Joined: 06 Dec 2019, 11:56

Re: Come on post your project please.... fieldstrength meter

Post by Taurus Flyer »

Oh, b.t.w. that was the carrier wave of ny 4 channel double triode transmitter I made a few years back, combined with a four channel superregen receiver.
schema buizenzender externe modulatie.gif
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Taurus Flyer
Posts: 28
Joined: 06 Dec 2019, 11:56

Re: Come on post your project please.... fieldstrength meter

Post by Taurus Flyer »

Phil_G wrote: 21 Oct 2020, 11:13 Excellent thanks Cees, great to see the old-tech valves still in use ;)
Yes Phil, I am glad with the transmitter, I also have my 4 channel double simultaneous transmitter, 50 years old functional for several receivers and actuators. Building a vintage glider and boat now but, not in a hurry.
Both transmitters and receivers combo's do have more than enough range to fly.
The old double triode's ECC81, ECC82 and ECC83 can have 6,3 or 12,6 V (DC-AC) heater tension, easy to combine with a 12,5 VDC NMHi battery. That was why I did use this double triode to design the MOPA (Master Oscilllator and Power Amplifier, ahum ;) ;) ) for this transmitter. The ECC82 was best choise for this task. The converter efficiency is about 85 %. All enough for several hours of functioning.
All receivers of own design, one 4 channel and several single channel, superregens but with added an antenna signal amplifier and tone selective by Schumacher filters, relay/relayless as in the past.

Cees
Martin
Posts: 744
Joined: 16 Feb 2018, 14:11
Location: Warwickshire

Re: Come on post your project please.... fieldstrength meter

Post by Martin »

Are you still using a real HT battery, or some kind of hidden step-up boost converter?
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Shaun
Posts: 1048
Joined: 15 Feb 2018, 21:49
Location: West Yorkshire

Re: Come on post your project please.... fieldstrength meter

Post by Shaun »

We have printable templates for a range of old HT batteries on www.singlechannel.co.uk.

I print them out on thin card, a bit of origami and glue then use multiple PP3 batteries in series to get the required voltage.

Shaun
Taurus Flyer
Posts: 28
Joined: 06 Dec 2019, 11:56

Re: Come on post your project please.... fieldstrength meter

Post by Taurus Flyer »

Martin, I have an original battery, 100 VDC. Copied the outside and let it print in a copy-shop.
When I turn the battery you see the converter and 12 AA penlights stillm in development stage.
The 4 - tone oscillator is at the backside of the circuit board, only the pot core(?) coil is right on top visible.
Picture two the front side the way it is now.
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