2703	2009-02-15 15:07:15	Ketner, Kenneth	Comments on PULGA Flea minimal xcvr
Message	Date	From	Subject
I finally had success with the Flea xcvr using the circuit board as given on the net and in the last issue of SPRAT. It seems that mine likes only certain particular transistors. I had tried some of the smaller tabbed transistors, such as the one in my Incher kit from Dan's Small Parts. When I tried a 2N3553, it was like the sun came up. I had hearty regeneration with the RX all across the narrow range of my VXO. And I had about 1 watt output using a 12 VDC gelcell. This particular transistor is a medium metal can type 7 mm in diameter and 6 mm high. I have heard many good signals from my Butternut ground-mounted vertical with it. I haven't tried a qso yet because I want to rig an antenna tuning unit to get the most of that lone watt. I also have followed the FLEA net process for building it up from just an Incher kit. Starting with one of Dan's incher kits, I got the TX function goin, then added 10K R in the emitter leg, slapped on an amp, and no RX. Eventually I changed that transistor to a 2N3553, and now it is a happy transceiver. It would be interesting to know what parameters of transistor are encouraging to the regen RX function and the power osc TX function within the FLEA. Has anyone else had experience with better or worse suited transistors for this circuit? Ken Ketner KA5ELD, GQRP 809 PO Box 65135 Lubbock, TX 79464-5135
2704	2009-02-15 16:03:05	Stephen Wandling	Re: Comments on PULGA Flea minimal xcvr
Ken, This is great news. I am eager to know what transistors you tried before the 2N3553? You also mention using a VXO. It was my intention to experiment with a VXO, once I felt I had the basic rig working, but I never felt confident that I had accomplished that, even though I had a 1000 mile QSO on 40M. The transmit was not the problem, rather the receive just didn't seem to be working as designed. The signals were there, but very weak, and I had to add additional audio to hear them. You mention that you "followed the FLEA net process for building it up from just an Incher kit" Is there a site that covers modifying an Incher to become a Flea? As you know, in the Sprat document, Joan Morros, ea3fxf, mentions trying a 2SC2988, 2N5909 and the 2N3866. In an exchange here on this list he recommended the 2N3866 over the other two, for better receive function, but with a reduction in transmit power. The 2N3866 is the only transistor I have used. You may be aware of my Flea site on QRPedia.com? http://www.qrpedia.com/book/200812/flea-catalonias-answer-pixie Its more or less my learning path, trying to get the Flea to function. Lots of folks have dropped by the page and left comments, including Eduardo, ea3ghs, who has worked with Joan on this design. Once again, great job. I'm glad you kept plugging away! 72 Stephen VE7NSD Ketner, Kenneth wrote: > I finally had success with the Flea xcvr using the circuit board as given on the net and in the last issue of SPRAT. > > It seems that mine likes only certain particular transistors. I had tried some of the smaller tabbed transistors, such as the one in my Incher kit from Dan's Small Parts. When I tried a 2N3553, it was like the sun came up. I had hearty regeneration with the RX all across the narrow range of my VXO. And I had about 1 watt output using a 12 VDC gelcell. This particular transistor is a medium metal can type 7 mm in diameter and 6 mm high. I have heard many good signals from my Butternut ground-mounted vertical with it. I haven't tried a qso yet because I want to rig an antenna tuning unit to get the most of that lone watt. > > I also have followed the FLEA net process for building it up from just an Incher kit. Starting with one of Dan's incher kits, I got the TX function goin, then added 10K R in the emitter leg, slapped on an amp, and no RX. Eventually I changed that transistor to a 2N3553, and now it is a happy transceiver. > > It would be interesting to know what parameters of transistor are encouraging to the regen RX function and the power osc TX function within the FLEA. Has anyone else had experience with better or worse suited transistors for this circuit? > > > Ken Ketner > KA5ELD, GQRP 809 > PO Box 65135 > Lubbock, TX 79464-5135 > > > > ------------------------------------ > > Yahoo! Groups Links > > > > > -- "You never change things by fighting the existing reality. To change something, build a new model that makes the existing model obsolete." -- Buckminster Fuller "First they ignore you, then they ridicule you, then they fight you, then you win" -- Gandhi
2705	2009-02-16 17:59:30	rheslip	Re: Comments on PULGA Flea minimal xcvr
I am interested in the tuning range of the Flea VXO. I speculated it would be quite narrow since the crystal is in a tank circuit. The Flea is a very clever design. I may try one too. Great blog there Stephen ! Rich VE3MKC
2706	2009-02-16 23:25:51	Stephen Wandling	Re: Comments on PULGA Flea minimal xcvr
I've never thought of the Flea as having a VXO, although I initially thought it might be possible to incorporate one. C3 is used to first peak the tank circuit, and then it's adjusted for clean keying. The potentiometer ,V1, in the emitter circuit can then shift the frequency approximately 1 Khz. I think of C3 as the regeneration control and V1 as a bit of RIT function. Thanks for the kind words. I have taken a breather from my Flea project, but expect to get back to it soon. I found I was confusing 'minimalist' with 'miniature', and had crowded parts onto a very small board making experimentation pretty hard. I've just been given a few FT-243 rocks for 80M, and I will abandon the little 'receive' type plastic trimmer I was using for C3. I also have some silver mica caps of appropriate voltage coming, so problems of stressing the caps in the tank circuit will be taken care of. Comparing the datasheets for the 2N3553 that Kenneth found to work well, and the 2N3866 that I have been using, I don't see too much difference. I have just found info on Dan's Small Parts site that he supplied either the MRF472 or the 2SC2075 with his Incher kit. I will take a look at their datasheets tomorrow. The MRF472 is what Dennis Monticelli used in his original Cubic Incher, which the Flea is based on, but Dennis was not trying to achieve any receive function. At the moment, determining what the critical conditions are for good reception is
2707	2009-02-17 10:32:35	Kenneth Ketner	Re: Comments on PULGA Flea minimal xcvr
There is a web page the PULGA designers put up at: http://ea3fxf.googlepages.com/flea I followed their discussion on how to develop a transceiver from the basis of an Incher tx. My experience was that I could get an Incher tx to transmit just fine, but by using the Incher kit specified transistor, I got no rx function. I had a nice pile of "pulled" (recycled) 2n3553 s, so I finally got around to trying that one. I think the one specified in the PULGA design is rather like the 2n3553. I am going to order one of the specified type and compare with 2n3553. I can send a 2n3553 to a devoted PULGA experimenter if I get a self-addressed return envelope or small box suitable for shipping a transistor (or maybe just postage, and I pick a small box). My mail address is -- PO Box 65135, Lubbock, TX 79464-5135. I'm afraid I am not an engineer, just a learner when it comes to electronics. But ain't it fun to fiddle around until it works? At lest I am learning the difference between a Coal-Pit oscillator and a Heartless oscillator. -- Kenneth Laine Ketner Paul Whitfield Horn Professor Institute for Studies in Pragmaticism Texas Tech University Charles Sanders Peirce Interdisciplinary Professor Anita Thigpen Perry School of Nursing Texas Tech University Health Sciences Center MAIL ADDRESS: Institute for Studies in Pragmaticism Texas Tech University Lubbock, TX 79409-0002 806 742 3128 Office email: kenneth.ketner@ttu.edu Office website: http://www.pragmaticism.net Personal website: http://www.wyttynys.net
2708	2009-02-18 16:04:29	Stephen Wandling	Re: Comments on PULGA Flea minimal xcvr
Kenneth, Thank you for this. I am aware of their Internet postings, and I also subscribe to the Flea designers email reflector (in Spanish), radiofrequencia, and note that today they are discussing the "reproducibility" of the Flea design. An issue they have identified is that the specified transistors, such as the 2N3866, are now somewhat 'obsolete', and only manufactured in China and that their parameters vary wildly. I note that the data sheets for the 2N3866 and the 2N3553 show very similar parameters, with you achieving a good receiver function and I do not. And my 2N3866 appears to have been manufactured by Motorola (it has their logo M on it.) On the radiofrequencia list today, they specifically mention the advantages of "pulled" devices. I currently have 4 2N3688s and have an order in for 2 2N3553s (at $5 each!). I think it will be interesting to compare a 'pulled' 2N3553 with a 'new' one. I will send you a SASE, and accept your offer of a 'pulled' device. I also have some "2SC2988", mentioned by Joan in his SPRAT-FLEA.doc, which are NTE2511. Their specs, on the package, does not match the specs in the Japanese transistor manual. Eduardo has suggested re-designing the Flea to accommodate devices such as the ubiquitous 2N2222, which Joan agrees will work well on receive, but with a much, much lower transmit power. There is also discussion to experiment with some Japanese transistors, such as the 2SC2166. Stephen VE7NSD Kenneth Ketner wrote: > There is a web page the PULGA designers put up at: > > http://ea3fxf.googlepages.com/flea > > I followed their discussion on how to develop a transceiver from the > basis of an Incher tx. > > My experience was that I could get an Incher tx to transmit just fine, > but by using the Incher kit specified transistor, I got no rx function. > > I had a nice pile of "pulled" (recycled) 2n3553 s, so I finally got > around to trying that one. I think the one specified in the PULGA design > is rather like the 2n3553. I am going to order one of the specified type > and compare with 2n3553. > > I can send a 2n3553 to a devoted PULGA experimenter if I get a > self-addressed return envelope or small box suitable for shipping a > transistor (or maybe just postage, and I pick a small box). My mail > address is -- PO Box 65135, Lubbock, TX 79464-5135. > > I'm afraid I am not an engineer, just a learner when it comes to > electronics. But ain't it fun to fiddle around until it works? > > At lest I am learning the difference between a Coal-Pit oscillator and a Heartless oscillator. > > -- "You never change things by fighting the existing reality. To change something, build a new model that makes the existing model obsolete." -- Buckminster Fuller "First they ignore you, then they ridicule you, then they fight you, then you win" -- Gandhi
2711	2009-02-19 06:18:51	k5nwa	Re: Comments on PULGA Flea minimal xcvr