SDS100/SDS200: Heating Issues - Better RF Performance when first powered on.

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cellphone

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As we have been having some 700mhz issues stemming from high noise in the Phoenix area(lengthy discussion here https://forums.radioreference.com/u...ers/371579-sds100-initial-review-phoenix.html), I was doing some testing this morning. I noticed something very interesting. The SDS100 performs much better when it is first powered on after being powered off overnight. As time goes on, performance issues with noise get worse. Even though I am in Phoenix, none of my tests have been in extreme temperature conditions (i.e. not outside when it is 116 degrees). My testing has always been done in my air conditioned home or car.

This might be one of our issues with performance in Phoenix as we do run a little hotter here. :)

Notice the pictures. These were taken when testing with an external antenna:
9:04am when first powered on. -45dBm signal, lower noise level 643, receiving the data channel frequency 771.76875.
9:19am no signal, high noise level 33009, not receiving or decoding the data channel frequency 771.76875.
9:45am after being powered off an sitting in the refrigerator for about 10 minutes. -45dBm, lower noise level 421, receiving the data channel frequency 771.76875.
 

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RFI-EMI-GUY

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There could be a serious frequency drift problem with the receivers reference oscillator.


Being that this receiver draws significant power for the DSP, that "work" (volts x amps = watts) becomes mostly heat building up in the radio. The tiny remainder of the work that is not heat, is audio power, LO and EM leakage and LED photons.

The RF preamp thermal noise might be elevating, though I would expect a much more subtle sensitivity impairment unless the part fails.

Can you measure the temperature of the radio case?

Commercial gear operates between -30 and +60 C ambient temperature. The actual interior is elevated by the electronics. The TIA603D spec for LMR gear describes the degradation over temperature. It is safe to assume that public safety grade equipment will operate over the entire range. To get there requires heat sinks, careful design, temperature compensation of oscillators, $$$$ etc.

What has Uniden specified for operating temperature?

Sent from my SM-T350 using Tapatalk
 
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cellphone

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There could be a serious frequency drift problem with the receivers reference oscillator. Being that this receiver draws significant power for the DSP, that "work" (volts x amps = watts) becomes mostly heat building up in the radio. The tiny remainder of the work that is not heat, is audio power, LO and EM leakage and LED photons.

Jon and I measured temperatures of the radio in the past in this thread:
https://forums.radioreference.com/uniden-tech-support/371976-warmth-issue.html

I have noticed much higher temperatures on the antenna connector and USB port when operating while charging, but have not measured since.

It's interesting that you mention operating temperature and drift, as I was looking for specs in the manual after I discovered this issue. I was not able to find any operating temperature specs. I was also looking for temperature offset specs. The earlier cheapo NooElec SDRs had issues with drift, but the current models have ±0.5ppm TCXO.
 
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RFI-EMI-GUY

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Jon and I measured temperatures of the radio in the past in this thread:
https://forums.radioreference.com/uniden-tech-support/371976-warmth-issue.html

I have noticed much higher temperatures on the antenna connector and USB port when operating while charging, but have not measured since.

It's interesting that you mention operating temperature and drift, as I was looking for specs in the manual after I discovered this issue. I was not able to find any operating temperature specs. I was also looking for temperature offset specs. The earlier cheapo NooElec SDRs had issues with drift, but the current models have ±0.5ppm TCXO.

I have observed a tendency for manufacturers to ignore elevated temperatures in their designs. I had a ROKU streaming video device. The size of a hock puck, it had no ventilation holes. I installed it inside a cabinet under my TV, a cabinet with admittedly a +38C ambient but with circulating fans and ventilation. It failed withing a day or so. The failure was inability for the WIFI to generate a MAC address. It was toasted and back it went. I have an Fire Stick in its place, actually two and they survived, though they get very warm as well.

The current draw of 700-800 ma cited in the other thread , if true is astounding. Is that at full audio or when idle? Motorola SABER radios draw a small fraction of that when idle. I have had a SABER radio on the bench, pulling 2300 ma while performing transmitter adjustments that take time and the radio is merely warm. There is a lot of internal mass in the PA heatsink, adjoining modules and radio frame. So it gets warm, the heat is contained in the mass and it dissipates over time. The frequency hardly drifts at all during this because the TCXO is on the opposite corner of the frame.
 
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Ubbe

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If a basestation encounter interference to its receiver it switches the control channel to another frequency, usually its called an alternative control channel in the lists. Did you check that and other frequencies if they also had lost all receive signals?

The SDR chip itself are guaranteed to work at 85 degree celsius.

The Saber transmitting doesn't convert all energy into heat, most of it goes out the antenna as RF power and doesn't stay in the radio.

/Ubbe
 

RFI-EMI-GUY

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If a basestation encounter interference to its receiver it switches the control channel to another frequency, usually its called an alternative control channel in the lists. Did you check that and other frequencies if they also had lost all receive signals?

The SDR chip itself are guaranteed to work at 85 degree celsius.

The Saber transmitting doesn't convert all energy into heat, most of it goes out the antenna as RF power and doesn't stay in the radio.

/Ubbe
True, at 7.5 V, the SABER radio draws 17.25 Watts, so minus the 5 watts work, leaves 12.25 watts heat inside the radio. Which is still a lot.

The point is, has Uniden has included sufficient thermal mitigation? Thermal mass won't help the Uniden very much if it is a continuous power dissipation. There needs to be conduction to the exterior plus convection.

If the degradation is reference oscillator drift, a better TCXO might be the fix. If there is a temperature sensor inside the chipset, a firmware upgrade might be able to fix it provided the oscillator frequency trim is directly within the control of the processor.

Maybe a big copper heatsink clamped on the antenna BNC jack!

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maus92

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Interesting. I haven't had any issues with my SDS100 that runs 24/7 in my A/C'd home that averages 80˚F, or when I take it on the road. The radio will shut down charging when I leave it running on charge in the Jeep with the afternoon sun blazing down on it. Still seems to receive normally.

Maybe iFixit will do a tear down and reveal the componentry.
 
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KevinC

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I wonder if leaving the headphone jack cover open and removing the piece of foam tape over that hole in the back of the case would help expel some of the heat? Probably not enough, but it couldn't hurt (other than it would no longer be splash resistant).
 

jonwienke

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Interesting. I haven't had any issues with my SDS100 that runs 24/7 in my A/C'd home that averages 80˚F, or when I take it on the road. The radio will shut down charging when I leave it running on charge in the Jeep with the afternoon sun blazing down on it. Still seems to receive normally.

Maybe iFixit will do a tear down and reveal the componentry.

How about iModIt? :D
https://1drv.ms/f/s!ApJIS-l4xqPtgvQQbjn2uujFCymvKw
 

DSC45

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Excessive heat

I’m finding that using the stock antenna seems to contribute to the receiver holding some of the heat. Using the SMA adapter with my RS800 antenna seems to absorb some of the radios heat through the adapter.

If I recall, Upman said during the testing that the radio would run ‘warm to the touch’.

Would be interesting to hear if your leaving your SDS100 on and running 24/7 !

Thank you.
 

iMONITOR

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It's not uncommon for the performance of various electronic components to degrade when heat reaches a certain threshold. That's why computers, CPU's, video cards have those mammoth heat sinks theses days. Many circuits will attempt to protect themselves from damage when heat levels become excessive by slowing down, or completely shutting down.
 

jonwienke

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Would be interesting to hear if your leaving your SDS100 on and running 24/7 !

I am, mostly inside wih occasional excursions to my truck. I'm using a SMA-BNC adapter, so that helps cool off the antenna connector...
 

KevinC

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To the OP, have you contacted Uniden regarding this issue?
 

eaf1956

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Interesting. I haven't had any issues with my SDS100 that runs 24/7 in my A/C'd home that averages 80˚F, or when I take it on the road. The radio will shut down charging when I leave it running on charge in the Jeep with the afternoon sun blazing down on it. Still seems to receive normally.

Maybe iFixit will do a tear down and reveal the componentry.

80 degrees OMG where is the A/C?
 
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