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Yaesu FT817
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Hi All
?I have a Yaesu FT-817 no mods,? factory original that works fine except that it has a strong carrier on 7.240 MHZ The carrier never goes away even when removing all? the antennas. Also very strong. Seems like it is internal generated. No other bands or frequencies are affected. The offending signal is very stable. Anyone else had any similiar problem ? Thanks? Robert |
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On Sun, 09 Oct 2022 12:39:15 -0700
"Robert Kovach" <r.kovach@...> wrote: Hi AllThe FT-817 has a reference oscillator at 22.625MHz. The receiver 1st IF is 68.33MHz, so at 7.24MHz the LO is at 75.57MHz or 61.09MHz. You also need another LO to mix down to 455kHz, that is at 67.875MHz. This is exactly 3x 22.625MHz, so it seems you are listening to 1/3 of the 2nd LO frequency. This could be leaking from the receiver somehow, maybe lack of decoupling on a problem with screening. Poking about with fingers can often reveal hot spots where signals are present if they should not be. -- Brian Morrison G8SEZ |
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On Sun, 9 Oct 2022 23:28:51 +0100
"Brian Morrison" <bdm@...> wrote: On Sun, 09 Oct 2022 12:39:15 -0700Scratch original calculation, brain fade. The receiver 1st IF is 68.33MHz, so for Rx at 7.24MHz the LO is at 75.57MHz. The 2nd LO used to mix down to 455kHz is at 67.875MHz. 75.57-67.875-0.455 = 7.24MHz The exact frequency depends on the mode, try USB and LSB and you will find a few kHz difference. My FT-817 does this, but the signal is not showing on the S-meter. It will be some leakage from one of the LO or mixer circuits -- Brian Morrison G8SEZ |
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Frank Zavada
On Sunday, October 9, 2022, 4:14 PM, Brian Morrison <bdm@...> wrote:
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Hi Brian Thank you for the info. The signal is only on that one frequency and I can live with that. I hate to start digging into the radio might do more harm than good.? ?Even if I did manage to locate the problem fixing it may be a tough one. I am an old geezer and my eyesight is not the best anymore. Probably best to just live with it Thank you for your input.....Robert? ?
On Sunday, October 9, 2022 at 04:20:22 PM PDT, Frank Zavada via groups.io <frankzavada@...> wrote:
On Sunday, October 9, 2022, 4:14 PM, Brian Morrison <bdm@...> wrote:
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¿ªÔÆÌåÓýHi Robert, ? The birdie on about 7238 kHz is well documented, for instance this bit from KA7OEI¡¯s website at : . ¡°One thing to keep in mind about birdies on HF frequencies is that they are usually so weak that normal atmospheric noise will cover them enough that they won't cause difficulty with communications.? Let's take as an example the well-known birdie on 40 meters on approximately 7.238 MHz (how's?that?for a band with no undesired carriers?)? When tuning this in with no antenna connected, this birdie sounds quite strong.? But (on my '817, at least) it is under 1 microvolt in equivalent strength (less than S1.)? If I connect the radio to an antenna, this birdie is pretty much lost under atmospheric noise. Now, were I using a mobile antenna or one of those collapsible whips that attach directly to the '817, the birdie would seem to be much stronger.? Why?? Two possible reasons:? The relatively poor antenna (face it, you aren't going to get a mobile or a collapsible BNC-mounted antenna that works anywhere near as well as a full-sized dipole) doesn't hear the signals on the band as well as a full-sized antenna - including atmospheric noise.? Also, an antenna that is mounted directly to the radio (besides being inefficient...) is more likely to pick up signals emanating directly?from?the radio. Speaking of the '7238 birdie, where does it come from?? It would appear to emanate from the BFO synthesizer, Q1031.? The fact that adjusting the PBT causes this birdie to shift would tend to validate this theory.? Another theory proposes that this signal is somehow related to harmonic of the 22.625 MHz reference oscillator interacting with the LO/IF in some manner¡± I also just got my 817 out and I have the exact same birdie. ? As you¡¯ll see there are a number of other birdies documented on that page as well. ? I also just checked one of my FT857¡¯s and it has the exact same birdie. ? 73¡.Eric VK2VE. ? From: [email protected] <[email protected]> On Behalf Of Robert Kovach
Sent: Monday, 10 October 2022 10:36 To: [email protected] Subject: Re: [ft817] Yaesu FT817 ? Hi Brian Thank you for the info. The signal is only on that one frequency and I can live with that. I hate to start digging into the radio might do more harm than good.? ?Even if I did manage to locate the problem fixing it may be a tough one. I am an old geezer and my eyesight is not the best anymore. Probably best to just live with it Thank you for your input.....Robert? ? ? On Sunday, October 9, 2022 at 04:20:22 PM PDT, Frank Zavada via groups.io <frankzavada@...> wrote: ? ? On Sunday, October 9, 2022, 4:14 PM, Brian Morrison <bdm@...> wrote:
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I checked with a friend of mine who has a FT-857 He also said that he can hear the same thing on 7,239. He said it is weak but still there. Guess that problem is the same with all the Yaesu radios of similar design. Just have to live with it...?
On Sunday, October 9, 2022 at 10:37:52 PM PDT, Eric van de Weyer <groups.io@...> wrote:
Hi Robert, ? The birdie on about 7238 kHz is well documented, for instance this bit from KA7OEI¡¯s website at : . ¡°One thing to keep in mind about birdies on HF frequencies is that they are usually so weak that normal atmospheric noise will cover them enough that they won't cause difficulty with communications.? Let's take as an example the well-known birdie on 40 meters on approximately 7.238 MHz (how's?that?for a band with no undesired carriers?)? When tuning this in with no antenna connected, this birdie sounds quite strong.? But (on my '817, at least) it is under 1 microvolt in equivalent strength (less than S1.)? If I connect the radio to an antenna, this birdie is pretty much lost under atmospheric noise. Now, were I using a mobile antenna or one of those collapsible whips that attach directly to the '817, the birdie would seem to be much stronger.? Why?? Two possible reasons:? The relatively poor antenna (face it, you aren't going to get a mobile or a collapsible BNC-mounted antenna that works anywhere near as well as a full-sized dipole) doesn't hear the signals on the band as well as a full-sized antenna - including atmospheric noise.? Also, an antenna that is mounted directly to the radio (besides being inefficient...) is more likely to pick up signals emanating directly?from?the radio. Speaking of the '7238 birdie, where does it come from?? It would appear to emanate from the BFO synthesizer, Q1031.? The fact that adjusting the PBT causes this birdie to shift would tend to validate this theory.? Another theory proposes that this signal is somehow related to harmonic of the 22.625 MHz reference oscillator interacting with the LO/IF in some manner¡± I also just got my 817 out and I have the exact same birdie. ? As you¡¯ll see there are a number of other birdies documented on that page as well. ? I also just checked one of my FT857¡¯s and it has the exact same birdie. ? 73¡.Eric VK2VE. ? From: [email protected] <[email protected]> On Behalf Of Robert Kovach
Sent: Monday, 10 October 2022 10:36 To: [email protected] Subject: Re: [ft817] Yaesu FT817 ? Hi Brian Thank you for the info. The signal is only on that one frequency and I can live with that. I hate to start digging into the radio might do more harm than good.? ?Even if I did manage to locate the problem fixing it may be a tough one. I am an old geezer and my eyesight is not the best anymore. Probably best to just live with it Thank you for your input.....Robert? ? ? On Sunday, October 9, 2022 at 04:20:22 PM PDT, Frank Zavada via groups.io <frankzavada@...> wrote: ? ? On Sunday, October 9, 2022, 4:14 PM, Brian Morrison <bdm@...> wrote:
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