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Michael Davis
Hi, while checking my transmit audio quality (getting muffled reports), I disconnected my Icom's antenna, set both the Icom and Bitx (on a 40 meter dipole) to the same frequency and listened to transmissions on the Icom. What I noticed was an S7 or 8 when keyed but not talking? In ssb, shouldn't the S meter be close to or at zero unless modulated by my voice since there is no carrier. Could someone please check for me in case it's some kind of thing that happens in such close proximity to each radio. Thanks |
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Your BFO may be off, that's why you are sounding muffled and that would also give you a carrier leak.
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Check the BFO frequency, mine is at 11.9985 MHz approx. At 09/04/2017, you wrote:
Hi, while checking my transmit audio quality (getting muffled reports), I disconnected my Icom's antenna, set both the Icom and Bitx (on a 40 meter dipole) to the same frequency and listened to transmissions on the Icom. What I noticed was an S7 or 8 when keyed but not talking? In ssb, shouldn't the S meter be close to or at zero unless modulated by my voice since there is no carrier. Could someone please check for me in case it's some kind of thing that happens in such close proximity to each radio. Thanks |
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Michael,
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Monitoring your transmit audio in station with a second receiver is notoriously difficult because of the proximity of the transmitter and monitoring receiver. Your transmitter is outputting watts and the monitoring receiver has sub-microvolt sensitivity resulting in the receiver being swamped by the transmitter output. What you are probably listening to are extraneous noises being picked up by the microphone which at close range (within your station) are strong enough to swamp your receiver. I have found that if you can have a nearby station monitor your transmissions, record them and then play them back to you this works a lot better, although it is a bit tedious. You make adjustments and listen to the result played back to you. Some of the more expensive transceivers have record facilities which make this a lot easier, but it works best if it is done at a distance. There could be a number of reasons for your poor transmit audio. I would check to carrier adjustment with respect to the filter passband. If that doesn't improve the transmit audio then have a look at the mic. Best of luck, Peter VK1XP On 09-04-2017 22:24, Michael Davis wrote:
Hi, while checking my transmit audio quality (getting muffled |
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No procedure has been described for adjusting the carrier (same as the bfo) frequency. One way is to add a 100pf variable cap at C103 (currently not stuffed) and adjust that cap for best performance. ?Could remove C102 if you need to go the other direction in frequency (alternately add an approximately 4uH coil at L5).? The other way is Pete's method of using CLK0 from the Si5351 to replace the analog BFO: ?/g/BITX20/topic/4703461? ? ?This method is preferred, as it could let you adjust the BFO using the tuning pot just like you currently adjust the BFO. ?But not yet fully supported, as I don't think anyone has posted a known good sketch for it yet, and the best way to wire CLK0 into the Bitx40 has not yet been resolved. ?(I suspect it should use the resistor network from the uBitx) On Sun, Apr 9, 2017 at 06:20 am, <pierre@...> wrote: I would check to carrier adjustment with respect to the filter passband. ?On Sun, Apr 9, 2017 at 05:51 am, Raj vu2zap wrote: Your BFO may be off, |
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Should read: ? This method is preferred, as it could let you adjust the BFO using the tuning pot just like you currently adjust the VFO. On Sun, Apr 9, 2017 at 06:55 am, Jerry Gaffke wrote:
This method is preferred, as it could let you adjust the BFO using the tuning pot just like you currently adjust the BFO. ? |
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Michael Davis
I am hoping my muffled audio is just some kind of input circuit mismatch with the new RS electret microphone element vs the original electret device. The more technical answers aren't ones that I understand or can change. These little electret capsules all look the same but have different electrical properties. I am trying to find the OEM specs so I can be sure I am using a very similar electret.
Sent from Mike's iPad WA1MAD |
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I was told some similar things in the beginning about my monitoring my muffled audio. On my SW receiver it sounded like I was talking into a fan. Look on the internet for something Called WebSDR. These are receivers around the country and the world. Using a nearby one of these is practically indispensable when testing your transmitted signal quality and range. Here is a link to the main page. Filter the band and location at the top of the stations list.-? And here is the link to the one I use most of the time.-??I can make it into this one in Arizona from Oklahoma. |
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Yes, the WebSDR online receivers are an excellent way of monitoring your transmit audio (I should have remembered that option) but be sure to use headphones and take precautions to keep the receive audio from getting back into your mic.
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This is another problem with in station transmit audio monitoring. Sub-microviolt receivers and local transmitters mean high system loop gain and it does not take much audio leaking back from receiver to mic to cause feedback in the system which again masks the true nature of your transmitted signal. Best regards, Peter VK1XP On 10-04-2017 08:13, John Smith via Groups.Io wrote:
I was told some similar things in the beginning about my monitoring my |
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So how did that get resolved? ?I assume that SW receiver was just too darn close. Jerry On Sun, Apr 9, 2017 at 03:13 pm, John Smith wrote:
On my SW receiver it sounded like I was talking into a fan. ? |
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I was a few things. The first rookie mistake was setting the receiver to a certain freq, and the BITX to the same and transmitting. The raduino was a few hundred Hz off and not calibrated yet. The close proximity of the receiver, received the signal much better than a distant one would have, sounding kinda weak and kinda fuzzy. I used the receiver like this before getting the BITX and knew to collapse the antenna, and turn off DX so as not to overload the front end signal amplifier. Searching for TX signal clued me in that I was a bit off intended freq. Assimilating a calibration fix has been nice. I only used it once so far. I also replaced the original mic capsule which improved the fuzzy oscillation sound a bit more. It did sound a little bit fuzzy and weaker on WebSDR with original mic. I don't know the specs on it. It came from a broken "The Clapper" wall switch, and is the same size. So the short answer is yes, it was too close.? |
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Michael Davis
I too made the "rookie" mistake. And by using the RS electret capsule, may have compounded the problem further. I did have my base rig antenna disconnected but there was still the ambient noise thing. Originally I had no audio, which led me to replacing my mic wiring back from the board and the electret. Went back to the original (which was still ok) and even in close proximity the audio sounded better, if not great. Will try the web sdr later. Still would like to know the original electret capsule spec. Anyone? Thanks to all
Sent from Mike's iPad WA1MAD |
Raj vu2zap