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Author Topic: Yaesu FT-1500M Spurious Emission Problem??  (Read 3507 times)
W4UXJ
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Posts: 5




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« on: June 15, 2003, 04:39:54 PM »

I have seen several reports that the FT-1500M puts out nasty spurs during key-up.  I understand that it is only for a few milliseconds when the PLL is moving from receive to transmit frequencies.  Not a big problem for voice operation but a nasty problem for packet or other rapidly keyed operation.  It is of sufficient power to cause area-wide problems.  I also understand that Yaesu does not or will not acknowledge that such a problem exists.  If you look at the signal after key-up, it looks clean so maybe that is what the FCC saw and approved.  But the spur is there only during key-up.

Does anyone know more about this?  Is this for real or is it a hoax?
73
Marvin
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ANULLRETENTIVE
Member

Posts: 60




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« Reply #1 on: June 15, 2003, 08:56:44 PM »

I have a lab grade spectrum analyzer and an FT-1500. I'll take a look and let you know, but please cite where you got this information and under what conditions this happens.
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W4UXJ
Member

Posts: 5




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« Reply #2 on: June 15, 2003, 10:46:09 PM »

Thanks for your interest and concern.
I have lost the e-mails with the gentleman that told me about his two 1500's
that had the problem.  He was using it on packet so it came up very
frequently and so caused a lot of problems.  It is only during key-up that
it takes place so it might be difficult to catch on the spec anal.  Good
luck and thanks.

73

Marvin
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KA5S
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Posts: 229




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« Reply #3 on: June 15, 2003, 11:31:16 PM »

I also noted this problem about 7 years ago on an FT-50RD. I told Yaesu about it (their representative was a member of our radio club) but I do not know if it was ever addressed in the design.

Cortland
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ANULLRETENTIVE
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Posts: 60




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« Reply #4 on: June 16, 2003, 03:30:29 AM »

Well Marvin, here's what I found.

Actual carrier frequency that I transmitted on was 146.550 Mhz at 50 watts into a 50 ohm load. The analyzer sampled this and was measured at -19.7 dBm, sweep time was 20 millisec.

Spurii was noted at 147.600 at -24 dBm, which is only 4.3 dBm below 50 watts, or around 17 watts (guesstimate) RF out.

Next spurii was noted at 147.300 at -32.4 dBm. Then there was a whole cluster of spikes between 146.057 and 146.110 Mhz, the highest being -25.7 and the lowest being -28.1 dBm.

Now sweeping at only 20 milliseconds isn't going to capture all the spurs, but this sure gives you a good snapshot of the crap that is coming off the antenna at significant power! This is a major problem for the FCC. Most commercial gear isn't supposed to bring up the power amp untill the PLL has settled and locked. This prevents the spurs from being transmitted. But I guess for fast transit time between tx and rx and the extra circuitry cost of switching the P.A. on after the loop has settled, it behooves the amateur radio manufacturers.

P.S. I only measured inband, 144 to 148 Mhz. I wonder what else is going out above and below these freq's?
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KB1GYQ
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Posts: 29




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« Reply #5 on: June 20, 2003, 12:23:11 PM »

Just a guess, I'll check later, but there may be an option on the service menu to change the keyup delay. I'll post what I find.
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KC8UNR
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Posts: 4




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« Reply #6 on: June 18, 2004, 04:54:39 PM »

I just found this post while looking around, yes this is true, I had to have aes fix mine.  The tech said there is a overheating problem, then things go bad from there and it doesnt matter what power.  When it over heats it goes way off freq.  Mine was almost 1mhz over at times.  The tech also said he has seen problems with spurs without the overheating.  I got rid of mine after it was fixed. good luck
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