Regenerative Comunications RCVR Mute

[xe1yzy]

Guys...

What is the right way to "mute " or put in "stand by" a regenerative homebrew comunications receiver?

Thanks in advance!

[W3RSW]

Depends on whether your receiver is solid state or tube.  Assuming your using a T/R relay that is dpdt which switches the antenna from transmitter to receiver and grounds the receiver on transmit, the next step is to mute the audio. 

In a tube rig, switch on transmit, a much more, say - 24 Vdc,  negative voltage on the grid of the regenerative detector or the following audio amplifier stage.  Check the tube tables for a good cutoff voltage.

It might be interesting to see if you can get a stable audio  side tone during transmit by not quite cutting off the detector tube and not quite squelching the audio.

If your T/R relay has extra contacts, you could simply open the supply rail on transmit to a couple of receiver stages in a lower voltage solid state rig.  Possibilities are many.

[xe1yzy]

Hi Rick,

Well, yes thats the point, could be great if I can monitoring my sending  trough the reciever, or at least dont have retunning each time when I go back to RX...

 is a tube rig, working with a 6SN7, but I have some other options, lets see what I can found, I has been reading a lot about the subjet , and I want to know if  its true that we can have achive good performance with a regenerative rig.

Best regards

Pedro

[W3RSW]

Hi Pedro,

Yes, a nearby transmitter probably does pull a regenerative receiver off frequency if tuning is not precise and the detector stage is unstable.

There have been a few recent articles about regenerative receivers with separate local oscillators.  I don't recall exactly but I think "Electric Radio" had at least one in the last couple of years or two.

 In the August 2007 issue W0ENE describes a five tube regen. using very solid National PW dial drive, a 6J7 as the detector with a 6J5 crystal controlled separate local oscillator for first conversion. This is now a quasi-superhet and feeds the real regenerative detector which is 1/2 of a 6SN7.  Next stage audio amp is the other half of the 6SN7.  Additonal audio amps are a 6SQ7 and 6V6 AF output to speaker transformer or phones.  The power supply is outboard. He uses it for regular check ins on a 40 meter net and is very pleased but does say it lacks selectivity of a "real" superhet.

He does not say how he T/R's it, but I imagine in the usual way.

[WQ9E]

If you are trying to use it as a monitor for CW, I would have the relay either ground or add significant attenuation to the antenna input as needed to prevent the detector from "locking" to the transmitter frequency and then have another relay pole switch in an auxiliary audio gain control to set the desired audio monitor level.

For this to be successful all voltages to the detector stage, including filament voltage, need to remain stable during transmit.  With a high power transmitter you may need to use regulated DC on the detector filament if your line voltage isn't "stiff" for the radio room circuit.

[W3NE]

Excellent articles on regenerative receivers have been written by Vern Yeich, KB3RQE and published by Electric Radio. They are included in a bibliography I compiled that reflects my particular interest in superhets with regenerative detectors but also includes most important early material by Grammer, et al as well as recent articles of which I am aware. See attachment.

WQ9E makes good points about regen Rx stability and his suggestion to short the antenna or attenuate the RF input, leaving the regen circuit alone, are well taken. In these days of direct digital conversion, roofing filters and so forth, the performance of a simple regenerative receiver can provide quite good performance considering its simplicity, if it is correctly operated.

Bob - NE

[KM1H]

I decided to let RCA do all the work and use a RAK/RAL and performance is amazing considering the mid 1930's design.

I also have a National SW-58 but havent taken that past some listening on BCB and 75M AM and letting its PP 45's tickle a very early National 10" speaker that came with the FB-XA Ive had for several years.

Carl

[VE3LYX]

I use a regen quite a bit on 80M. I built a box from wood. (period correct) Inside I have a light switch. The new kind with the wide flat push toggle . I drilled two holes in the top of the box. One over each end of the switch . I inserted a wire with the top bent flat in a circle in each hole so it sits on its end of the switch. The two flat bent circles sticking up. I wired te B + for the 12sn7 to this switch . When I am on receive I push the button  or flat bent wire on the one side and my Regen with tube glowing jumps to life. When I transmit I push the other button or flat wire and cut of the B plus . Works absolutley perfectly and has for several years. Picture coming right up momentarily.  

[xe1yzy]

@Rick, well yes, the idea is keep it at simple as posible without ending in a Superhet, ( like the "simple X" from ARRL handbooks who use a regenerative detector), Im going to take a look on the articles of Electric Radio Thanks!

@Rodger, thanks for the ideas, IF I could monitor my sending on CW using the receiver will be great, but the stabilty of the circuit its my goal, I planning use only a 100 w trasmitter or so, but I like your idea to use a regulated DC

@Bob, WOW!, thanks for the info, a lot of information to read, nice job!

@Carl, nice rigs I would love to see a picture!

@Don, HI!, thanks for your answer, and also to let me  know that you are using a regenerative as a comunication receiver, great!, I really love to see a picture of the complete station!,your T/R box idea looks great.

Thanks to all

[VE3LYX]

Here it is.The TX is rock controlled and has provision for modulation (dead centre bottom) It is a single tube 50l6 but must be used with a modulator (audio amp) to screen modulate. Mostly I use it on CW. The regen on the left I often use on AM. Last night a good friend was on 80 . He had broken his AM rig and had to use SSb to work the other  AM stations. I quickly turned on the Regen and could copy both with ease by carefully setting the regen control right on the cusp. My heathkit recvr could do it but it was a constant battle correcting so I could hear both. The Regen  could copy both just fine. I know he will be back on AM in a day because he is just that kind of fellow. I just was basically reading the mail but did give it one crack at getting in. Obviosly I wasn't heard.
This regen is far and away the best I ever built.  It is a 12sn7 (or 12SL7) single tube , conventional tickler,  cap coupled antenna, Rheo regen control, audio filter of sorts which does a good job when noise levels are high and plug in coils.
Believe it or not it runs on a 12 inch 12 turn loop antenna sitting in the window. I have many contacts with this station on CW using both units  and have often worked the regen in conjunction with my DX60B TX for AM.
I have another AM transceiver I built homebrew with a similar set of circuits and a screen modulated 50L6. I didnt use this particular regen circut for it and am sorry I didnt. Since it is the same tube that is about to change. This regen runs on Battery power. Ten 12 volts in series with a filment take off  after the first 12 volt. Very quiet power! Charges with a line cord and one diode when I need to boost it between ops. Actual plate voltage when running properly in regen mode is around 68V if memory serves me.
Sorry to be so long  but anyway there is the station.
Don

[xe1yzy]

Good Morning Don,

Thanks a lot for the picture and nice description, your set up  really looks great!, nothing compares whit the moment on a QSO when you said "....Rig here are homebrew" even if you are just crossing your county! right?

Again many thanks!

Pedro XE1YZY

[VE3LYX]

Pedro,
I owe you a big thank you.  Your post inspired me to go back at one unfinished homebrew project. My small 2 tube transciever. 56 and 42 tube. I bit of testing and a lucky guess and I have it working since adding the audio PA which also works as a RF PA when the switch is on TX.  I had to fudge the interstage audio in the regen side with a normal hi imped to 8 ohm one that was in my junk box when it really wants 1 to 1  but it now works. I have also had a real pentode in here (not grounded supressor ) and was able to supressor grid modulate it although currently I dont have that function. This one mutes when you throw the switches to TX. Thanks for the inspiration.
Don

[xe1yzy]

Don,
We are even!, your pictures encourage me to make a station like yours hi hi, so you don't own me nothing!
Maybe a CW QSO when I finish mine, Ok?

Regards!

Pedro

[VE3LYX]

Sounds good.
Don

[WU2D]

Hi Pedro,

Of course building a regen for the hams bands is great because you can get the band spread out over the whole dial. Everything will work better with a transmitter if you build the regen on a metal chassis and put it into a metal box and you use a good vernier on the tuning cap. This gives you a shot at getting some TX-RX isolation. The method of switching the input and killing the audio with muting bias as described above is good for an AM station. For CW some more playing around is required if you want sidetone.

I have an idea for you to try. Instead of disconnecting and grounding the regen antenna connection on TX, connect the grounded terminal instead to a 500 Ohm potentiometer to ground. Then with an extra set of contacts, change the detector's screen voltage (or triodes plate voltage) from critical to a higher voltage that causes the detector to not overload. Higher voltage allows the detector to be "stronger" and more like a direct conversion receiver and the transmitter will not overload and pull it as much. If this voltage is also adjustable (typically if your critical voltage for good sensitivity for CW is 20 to 40 VDC) the higher voltage to get a good side tone will be from 60 to 150V.

Of course the higher voltage will "push" the regen off frequency.

This is where in 500 Ohm input pot comes in. So now you play with the input pot until the sidetone comes back on frequency in TX with the higher voltage. So what you are doing with the antenna pot is "pulling" the regen back on frequency so that it works like a sidetone.

By the way, a regen in a completely sealed metal box with a pair of headphones called a station monitor was the basis for being able to get your transmitter and station regen on the same frequency in the late 1920's and early 1930's. You basically marked the dial on the sealed box regen for the center of the band. Adjusted your transmitter for zero beat or a low tone in the monitor. Then tuned your regen until it heard the weak oscillation of the sealed regen. Now both TX and RX were "in the band" and close to the same frequency. The station monitor also was your sidetone and chirp and CW quality monitor.

Mike WU2D

[KM1H]

@Carl, nice rigs I would love to see a picture!

http://www.virhistory.com/navy/rcvrs/rak-ral.htm

http://www.radioblvd.com/WWII-PostWar%20Hamgear.htm

[xe1yzy]

Hi Mike, Thanks for your tips!, I got the idea, let me doit a see what hapends!

@Carl , thanks for the links!

Pedro XE1YZY

[xe1yzy]

First smoke test of my  homebrew HF regenerative radio receiver, build from scrap following the ideas and desings of Charles Kitchin N1TEV,

http://www.youtube.com/watch?v=O9QQ6GkiINQ

[N0WVA]

Looks good, I thought it was a tube rig until you showed the back of it.

One thing I found out is the FET regens require only a one turn link for feedback and a one turn link for antenna. The grid or "gate" coupling capacitor should be as small as possible, I make it by simply wrapping a couple turns of enamel wire over the hot tank lead that goes to the tuning cap.. Its probably about 1-3 pf. This works FB for CW and SSB so the tank doesnt pull and "warble" on the strong signals. For AM, stick with 47pf or more.

[xe1yzy]

Thanks, well yes the original idea was go on tubes, but I prefered go solid state because the receiver on tubes are simple yet , but  need a very good desing on the power supply , and I want to keep the things simple and effective as possible, this radio can go for many many hours with only one 9V battery, without any "hum"

This radio use a simple "poor man" varactor for fine tuning, and this allow to just "turn off" the rig on transmit, and turn on again for RX, the audio quality on AM are great, due to the fact that the radio amplifies the desire frecuency without any conversion or mix, this allow a truly Hi Fi audion output

[WU2D]

Great job Pedro and nice video. FET regens are a lot of fun. I do find that they tend to push frequency a bit more than tubes when adjusting the regen control. Please publish your final schematic. One possible improvment would be to back the front panel with some foil or flashing. I find that a grounded metal front panel really helps regens stability wise.

73's Mike WU2D

[xe1yzy]

Hi Mike, thanks for your comments, following you will found the link to the schematics and circuit description, the only mistake on the schematics are the pin location on the MPF102, other wise the circuit  works very nice.

I dont make any modifications, I build the circuit on "Manhattan Style", in order to have room for further experiments

http://www.electronics-tutorials.com/receivers/regen-radio-receiver.htm

BTW, Happy New year to all!!