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Old 04-23-2013, 3:43 AM
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Default J725M vs M7100 sensitivity

Comparing a Jaguar 725M to a M7100 on 800 MHz, it seems like the M7100 is a little deaf. The J725M has a 'noise floor' reading of -138dBm, compared to the M7100 of -129dBm (both terminated with 50 ohm load), and the M7100 has a corresponding 9dB less sensitivity compared to the J725M. And for that matter, an Orion, 700p, LPE200 etc.

Has anyone else made this observation? I guess there's precious little that can be done about it, since the M7100 front end and IF strip have absolutely no tuning points, physical or software.
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Old 04-30-2013, 3:33 PM
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That number, -138 dBm, seems awfully low. I've NEVER yet seen any mobile or portable radio that had anywhere near that kind of sensitivity.

I've seen -131 on a particularly sensitive VHF XTS5000, but even at that level we're talking about only .06 microvolts. Which is amazing for a non-satellite product.


Are you sure that the 725 is really showing a receiver sensitivity of -138 dBm, on frequency?

I'd suggest rechecking that and inserting a narrowly tuned bandpass filter between the signal generator and the radio. I think it's got to be opening up on a spur or harmonic coming from an outside source or your generator's LO.

What kind of generator are you using to perform the test?

I can take my R&S generators down to -140 but at that level, RF leakage from inside the unit's case is stronger than the RF port's output. While I could pad down the output a few hundred more dB if I wanted to, by stacking attenuators, it wouldn't do a bit of good if the receiver under test is hearing the signal leaking through the chassis.
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Old 04-30-2013, 3:59 PM
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What are you using to indicate your RSI?.. The built in RSI on the radio? or are you using some sort of quieting / Sinad set up?
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Old 05-01-2013, 5:13 PM
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That -138dBm figure for the J725M & -129dBm for the M7100 isn't an actual noise floor measurement, it's the radios own FCC menu display under 50-ohm terminated, no input signal condition. Note that the difference between -138 and -129 dBm is 9dBm.

Then each was put across a HP 8924 to determine 12dB SINAD figures, and the J725M was 9dBm better than the M7100; 20dBQ findings were the same too. 9dB more sensitive and 9dB difference in FCC menu RSSI with no input signal - coincidental? Other 800/900MHz units here also turn in broadly comparable sensitivity figures, generally being a decent margin more sensitive than the M7100.

Its those findings that leads to the question: is the M7100 is inherently a little deaf?
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Old 05-02-2013, 8:23 PM
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No it is not deaf, Your's apparently needs a hearing aid..
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