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Author Topic: Kenwood TS480 Dynamic Range  (Read 1501 times)
KB7FSC
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Posts: 93




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« on: October 29, 2017, 06:19:32 PM »

Is anyone aware of the dynamic range numbers for a 480 with installed crystal filters? Sherwood has test results for a 480 without crystals, but I’m curious how much difference installed crystals would make on these test results.

Wane - KB7FSC
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W1VT
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« Reply #1 on: October 31, 2017, 11:33:25 AM »

ARRL members can download Product Reviews with test results.
June 2004 QST has the test data.

With 5kHz spacing and 500Hz filter installed, the two tone 3rd order dynamic range is 75 or 76 dB.

Zack W1VT
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KB7FSC
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« Reply #2 on: November 04, 2017, 03:24:49 PM »

Thanks Zack! I also found some additional information from Kenwood in their in depth 590sg manual. They had a graph comparing dynamic range against the 590sg, 590s and 480 with 500 hz filter. I appreciate you taking the time to respond. 73!

Wane - KB7FSC
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WD4ELG
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« Reply #3 on: November 04, 2017, 06:22:49 PM »

Wane, I had the 570 and I have the 480.  What did it say regarding the 590SG compared to the older rigs?
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KB7FSC
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« Reply #4 on: November 05, 2017, 11:58:40 AM »

Wane, I had the 570 and I have the 480.  What did it say regarding the 590SG compared to the older rigs?

The in depth manual for the 590sg had a graph comparing the 590sg, 590s and 480 with 500 hz crystal. I didn’t see anything comparing to the 570. 

FWIW, I’m considering a new radio, and the dynamic range is just one of the many items I was researching regarding a new radio. In playing with my 480 which has both a 1.8 khz and 270 hz filter in the cw ss contest this weekend, I have to say I’m very impressed with my 480. The 270 hz crystal really allows for some great selectivity.  I’m researching and wondering how much more difference I’d see with a 590 sg, Icom 7300 or potentially a ftdx 5000.  Of course, each of those rigs has other pros/cons and dynamic range is just st one item to compare.

73,

Wane - KB7FSC
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K8AC
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« Reply #5 on: November 10, 2017, 07:35:53 AM »

Wane - I was just reading through your comments and wanted to point out something about the dynamic range testing.  What it looks at is what happens in the receiver with two test signals that are outside of the bandpass of the narrow IF filters.  There should be little if any difference observed in IMD in the 480 using a 270 Hz filter or a 500 Hz filter.  The narrow filters in the 480 are in the second or third IF (don't recall the number of IFs in the 480).  The filter in the first IF in the 480 is likely in the 12-15 kHz range and that stays the same no matter the bandwidth of the narrow filter you're using in a later IF. 

So, while you wouldn't be hearing the test signals used, the mixer and amplifier stages prior to your narrow filters would be seeing the strong signals because they got past the wide first IF filter.  In a contest situation with the band full of strong signals, you'll hear the IMD products from all the strong signals no matter how narrow the filter you use. In a CW contest, it will sound like random bits of CW dots and dashes - just random noise, but not white noise.  In most cases, you can dial in a few dB of receiver attenuation and the noise will suddenly disappear. 


A better solution is to install a narrower filter in the first IF, such as supplied by Inrad for a number of popular radios.  Unfortunately, for smaller radios like the 480, that's not a practical solution.  I ran into the IMD problem with my old Icom 756 Pro III many years back and installing the roofing filter in that transceiver eliminated the IMD problem for me. 

In any case, any receiver with a close-spaced IMD rating of 80dB or higher should be perfectly adequate in all but the most difficult situations.  Both Sherwood and W8JI have stated that and I've found it to be true for the locations I've lived in. 
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KB7FSC
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« Reply #6 on: November 14, 2017, 05:43:01 PM »

Floyd,

Thanks for the comments regarding dynamic range.  Your description is really well written and it helps me "connect the dots" better with regards to what dynamic range is and isn't. 

I hadn't ever noticed the random dits of cw before, but a few days ago I experimented with a dx pileup.  There was a weak dx station with several s9 +20 stations close by.  Just like you said, even though my 270 hz filter blocked the loud station when he was transmitting, I did get some random dot type noises.  Interesting enough, NR2 actually covered up some of those IMD products when they bleed through.  I also played with attenuation and rf gain, and that helped as well.  In the case of the dx station, they were pretty weak, but adjusting the gain and utilizing NR2 made the weak station still very readable. 

That being said, I wouldn't give up my 270 hz filter.  It really makes a huge difference for cw, rtty and other digital modes when it is selected.  I'm considering a new radio with the Thanksgiving sales coming up, and it will be interesting to compare against my tried and true 480.

Thanks again for taking the time to explain!

Wane - KB7FSC
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