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good news / Bad news
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Baruch Atta
I have some good news and some bad news regarding my work on the Bitx 40v3. First, the good news.? I replaced the four caps that determine the frequency on the VFO, these are c91, c92, c94, c95 with NP0 grade caps.? The good news is that this made the VFO rock solid, no noticeable drift. Nice.? However, the bad news.? Now the frequency range is too low, even setting the c93 to the minimum.? But even worse, the sensitivity is now very low, not receiving any but the most loud signals. ? Now, I can probably fix the frequency range issue by removing turns from the coil.? But I am at a loss regarding the sensitivity issue.? Any clues? thanks Joe |
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Joe,
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In the process of changing the caps you may have done some damage to neighboring parts. Please check with a magnifying glass. A torroid lead may have broken off. 73 Raj vu2zap At 12/12/2016, you wrote:
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It could be that the T1 or T2 windings are shorted - f On Tue, Dec 13, 2016 at 10:25 AM, Raj vu2zap@... [BITX20] <BITX20@...> wrote:
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I had this problem with my rig. It turned out to be a bad variable cap, C93. I replaced it with a Murata yellow cap. I would guess that any good 2-33 pF cap would do the job. It would seem that C93 probably has mylar separators inside, and these are easily damaged by heat. This may not be the case for you, but it should be considered, especially if there has been a shift in frequency coverage...
I like the idea of replacing the VFO caps with npo units. Good job. john AD5YE ---In BITX20@..., <baruchatta@...> wrote : I have some good news and some bad news regarding my work on the Bitx 40v3. First, the good news.? I replaced the four caps that determine the frequency on the VFO, these are c91, c92, c94, c95 with NP0 grade caps.? The good news is that this made the VFO rock solid, no noticeable drift. Nice.? However, the bad news.? Now the frequency range is too low, even setting the c93 to the minimum.? But even worse, the sensitivity is now very low, not receiving any but the most loud signals. ? Now, I can probably fix the frequency range issue by removing turns from the coil.? But I am at a loss regarding the sensitivity issue.? Any clues? thanks Joe |
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Baruch Atta
Raj Yes, I was thinking of that.? But for me, it is better to put it away for a few days and both of us (me and the BitX) can cool off! Joe On Mon, Dec 12, 2016 at 11:55 PM, Raj vu2zap@... [BITX20] <BITX20@...> wrote:
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Baruch Atta
To the group: ?just to let you know that things are coming along. ? What I thought was a lack of sensitivity was just an out-of-band experience (out-of-body?) After I replaced my caps with NP0 caps, it seems that my range is 7.270 to 7.400 or so even with the var cap fully meshed.? So just the top top part of 40 meters.? Not good. ?but not so bad.? I could hear a station this afternoon, weak but weak also on my big rig. ? But the good thing is that the rig is solid on the frequency. ? I hooked up my oscilloscope and got a good signal from the DDS pin.? But I could not hear that on my big rig, perhaps because the wire connecting did enough to stop the oscillation.? Also, I sent out some smd caps to another user.? So my offer still holds, I will send you a few smd caps (1000pF and 150pF) if you send me a self addressed stamped envelope. But be aware and be warned: And your milage may vary. ? ?73, Joe W3TTT On Tue, Dec 13, 2016 at 2:07 AM, iam74@... [BITX20] <BITX20@...> wrote:
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Kenyw
I have a Flex SDR and recently here in Central Ohio I can count the number of signals across the whole 20 meter band on one hand.
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-----Original Message----- From: mvs_sarma@... [BITX20] To: BITX20 Sent: Tue, Dec 20, 2016 11:41 pm Subject: Re: [BITX20] Re: good news / Bad news
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May friends indicated that the propagation conditions are pretty BAD. we need to hold back before commenting on the Rx .
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I worked S75DX last night at 1 am on the bitx40 into a 51 foot doublet at 40 feet. - f On 21-Dec-2016 7:39 pm, "Kenyw kenyw@... [BITX20]" <BITX20@...> wrote:
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Kenyw
40 meters has been kind to me. I recently had a South African QSO. A record distance of 8380 miles on a G5RV. This was on a Flex 6300...I can't wait to try my new BITX40...I bought one just before the ordering was closed until the updated units come out.
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-----Original Message----- From: Ashhar Farhan farhanbox@... [BITX20] To: BITX20 Sent: Wed, Dec 21, 2016 11:00 am Subject: Re: [BITX20] Re: good news / Bad news
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I worked S75DX last night at 1 am on the bitx40 into a 51 foot doublet at 40 feet.
- f
On 21-Dec-2016 7:39 pm, "Kenyw kenyw@... [BITX20]" <BITX20@...> wrote:
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John,
I think polymer multi-film Philips make 3~27 Pf are more frequency stable then ceramic murata ! Yes they easily gets destroyed by excessive heat by soldering iron, & cannot be re-used. Hi ceramic-trimmers I have only used in BPF & LPF so far, but not yet in any oscillator or below XTAL. 'Repair & Reuse or Recycle E-Waste' On Dec 13, 2016 12:37 PM, "iam74@... [BITX20]" <BITX20@...> wrote:
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Maybe. It depends upon whether they are XR7 or npo. I used Murata caps because they are what I had in the junkbox. I think they are more generally available (and are cheaper) than, e.g. the Phillips ones. They work.
The best to use are mica trimmers or ceramic miniature air variables. These are hard to find reasonably. I probably will install some kind of DDS anyway. I just haven't built it yet! Hi. 73 john AD5YE ---In BITX20@..., <sandeeplohia12@...> wrote : John, I think polymer multi-film Philips make 3~27 Pf are more frequency stable then ceramic murata ! Yes they easily gets destroyed by excessive heat by soldering iron, & cannot be re-used. Hi ceramic-trimmers I have only used in BPF & LPF so far, but not yet in any oscillator or below XTAL. 'Repair & Reuse or Recycle E-Waste' |
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On 25/12/2016, iam74@... [BITX20] <BITX20@...> wrote:
got some leftover MINIMA digital dial PCB in my junk from first run, for those willing low jitter-noise. @ $ 1 including shipping international, Hi a set of 2 PCB (no exiter) will be happy if you ( or some else ) populate & use... PM me address. will need IF coding from 20 to 12Mhz, or vice-vera change Xtal to 20 Mhz ? circuit below marked red : Wishing you all a very happy Xmas time with bitx's. Happy homebrewing.
-- Please encourage recycling, reuse or repairing of E-waste. ?7?3? ?d?e? ?V?U?3?S?X?T? |
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Namaste, Sandeep.
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We could probably use paypal. I would be interested in 2 sets. It's easier than muppeting them, I guess. Use my e-mail address in the header, but don't send yours to the group, please! john AD5YE ---In BITX20@..., <sandeeplohia12@...> wrote : On 25/12/2016, iam74@... [BITX20] <BITX20@...> wrote: >got some leftover MINIMA digital dial PCB in my junk from first run, for those willing low jitter-noise. @ $ 1 including shipping international, Hi |
Raj vu2zap
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