[HBQRP] Fw: [Minimalist_QRP_Transceivers] Digest Number 433

[Arnie Grubbs]

Hi HB-QRP groupies..


I thought that some of you might be interested in this note from Peter Parker, about an

idea he has for a minimalist 10M FM rig...  seeings as how the 10 meter bands have

been hot the past couple of days.


Peter has had a number of nice minimalist QRP rigs that he has built, and put on YouTube

several Vids showing some of his creations and details of each step  of the

schematics.  While he has not done so with this 10m FM rig yet, he has put up

some DSB rigs and some CW rigs.. so I hope that he will do the same with this rig.


I hope if you are interested in this, or at least curious, you will take a look at some of

Peter's Vids..

http://www.youtube.com/user/vk3ye/videos
.  


73 - Arnie KA0NCR





________________________________________________________________________
1. The world's simplest frequency agile 10m FM transceiver (with repeat
    Posted by: "Peter Parker" parkerp at internode.on.net petervk3ye
    Date: Fri Oct 18, 2013 9:14 pm ((PDT))

(This rig has not yet been built, but there is no reason why it should not work.  As far as I know it's an original idea and you read it here first.) 

Transmitter (approx 100-200mW out): 

Mic Amp: BC548 + diodes for frequency modulator
Ceramic resonator oscillator: BC548 (using 10 MHz ceramic resonator pulled down to 9.9 MHz)
Frequency tripler: 2N2222
RF amplifer: 2N2222
RF amplifier: 2N3866, 2N4427 etc

Receiver: 

RF preamp: MPF102
Superregen detector: MPF102 (possibly with another device for a seperate quency oscillator)
AF amp: LM386

So far there is nothing unusual. 

The twist is as follows: 

Superregen receivers perform well with AM and WBFM signals.  However their performance is poor with NBFM signals (a lot of hiss and not much audio). 

ZL3VN has shown that superregens can be made to work with NBFM provided that a local RF oscillator is operated at the receive frequency offset by the quench frequency (can be either higher or lower)

I would suggest that a 10m FM superregen receiver have a 100kHz quench frequency. 

As it happens this is the same as the repeater offset.  So you leave the transmitter's ceramic resonator oscillator running during receive to provide the needed local signal. 
So no need for a seperate RF oscillator for NBFM and it should be reasonably stable,  using the ceramic resonator (at least for FM, not necessarily for SSB).  

My latest Beach 40 rig has a 7.2 MHz ceramic resonator which swings from 7040 - over 7300 kHz with an air spaced tuning capacitor in a single swing.  Hence it should not be too hard to get 167 kHz swing out of a 10 MHz resonator. 

29.6 MHz simplex could be harder to arrange - you would need to offset the tx oscillator by 100 Hz.  You could switch in capacitance etc or (probably easier) is to build another 10 MHz ceramic resonator oscillator that's switched in on receive (tripler probably not needed as 3rd harmonic should be enough).  If you do the latter I wonder if you'd hear WWV on 10 MHz (if you connected an HF antenna) due to beating of various signals? 

73, Peter VK3YE

















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