Montag, 5. Februar 2018

Comparing the IC-R8600 on VHF/UHF with other radios

Recently I treated myself with an Icom IC-R8600 receiver. Of course I wanted to know how it performs in comparision to other radios I have. Here is the result.

tl,dr;

The IC-R8600 is generally less sensitive than the two radios I compared with. That is to be expected, since it is a wideband, all purpose receiver, the other radios are more or less specialized to their purpose.



Comparing IC-R8600 vs IC-7400 on VHF

The Icom IC-7400 is my everyday VHF rig for weak signals, i.e. SSB and CW. I participate in contests with this radio.

Comparing VHF Beacons

I use a standard set of beacons to check conditions. Some of them so weak, that I can barely discern them in the noise, perfect for checking band conditions. Others are close by and loud.

The antenna is a horizontal WiMo WY-209 Yagi, 9m up above ground. No external receive amplifier. Both rigs were connected to this antenna via a 2-way coaxial switch (Diamond CX-201A). Cables from the switch to the two radios were not exactly same length/type, but nearly, the differences should be negligible.

Settings for both radios:
  • Pre-Amp on
  • filter set to 500 Hz width, steep slopes
  • AGC fast
  • HF Gain 100%
I am aware that the S meter of the IC-7400 is not very well calibrated, in contrast to the IC-R8600. So I gave my best reading and included also an 'Overall' evaluation (the O from SINPO code), ranging 1 (poor, not legible) to 5 (perfect copy). The 'Waterfall' column shows whether a signal was visible in the IC-R8600 waterfall display or not. The 'Rev' level of the waterfall display was cranked up to +10 dB so I could see some noise at all.

Here is the result in tabular form:


IC-7400 IC-R8600
Beacon Distance S-Meter Overall S-Meter Overall Waterfall
DB0MMO 122 km 2-3 4 0-1 3 -
DB0MFI 177 km 1-2 3 0-1 2 -
DB0JT 368 km 0-1 2 nil - -
F1ZAW 354 km 0-1 2 nil - -
DB0JW 194 km 0-1 2 0 1 -
DB0HRF 121 km 9 5 5 5 yes
Graves
Radar
280 km 4 5 1 3 yes


Conclusion:
The IC-R8600 is less sensitive than the dedicated VHF rig. This is no big surprise, since the 8600 is a wideband receiver. And it's still within specs, the IC-R8600 claims -10 dBµV (0.31µV), the IC-7400 claims 0.11µV (-19dBµV) in the 144 MHz range, although the difference feels larger than 10 dB.  But I have not made a precise quantitative measurement.

Unfortunately the waterfall display is useless for weak signal monitoring. My hope was to use it to monitor a beacon with the volume turned down and see (visibly) if it comes up due to better condx. Regrettably that does not work as expected. Except for the strongest signals (S3 to S4 and above) the waterfall registers any signal at all. Below that there is no trace of a signal. Most pure SDRs are better in that respect, because they scale the sensitivity over the waterfall gain better. I.e. the other SDRs are not more sensitive, they just make more out of the received data. So there is hope that Icom can modify the software to give us better sensitivity on the waterfall for weak signals.


Comparing VHF FM Repeaters

During this measurement the antenna was an omni-directional (vertical) Diamond SE-100, mounted above the Yagi in approx. 9m above ground. Same coax-switch, same cables. Rigs switched to FM of course...

I checked all VHF repeaters within reach, and without going into details, the result is consistent with the table above. Each repeater is about 2 to 4 S levels weaker on the IC-R8600 than on the IC-7400. In all cases the waterfall gave a clear line, so monitoring FM repeaters for activity will not be a problem. Of course no repeater was really weak... they were all at least S5 on the IC-7400. Readability (overall value) was 5 in all cases on both receivers.



Comparing IC-R8600 vs TM-D710E on UHF/FM

Since I have no SSB rig for 70cm I just did a brief comparision of FM repeaters against my Kenwood TM-D710E. 
The results are again consistent: the 8600 is less sensitive that the FM rig. The difference is smaller than on VHF, about 1 to 2 or maybe 3 S meter values. The comparision was difficult because the TM-D710 does not have a really good S meter to speak of.
Readability was 4 to 5 in most situations on the IC-R8600, only in two cases where the FM signal is barely above the noise, readability was compromised where I could still read the signal on the D710E.

Same antenna as on VHF repeater comparison: Diamond SE-100 in 9m above ground.



IC-R8600 on SHF beacons

Just for the fun of it I tried to listen to beacons on 23cm and 13cm. I had no big expectatiuons, but to my surprise I can hear a few very close beacons on both bands. The antenna was a 80cm long, vertical log-per, which is normally used for GSM/UMTS/LTE experiments. So not a high gain antenna, and vertical where all beacons are horizontally polarized. 
Again the beacons were too weak to leave a trace in the waterfall, but I could hear them fine and without problems.


Overall Conclusion

The sensitivity of my IC-R8600 is ok on VHF/UHF/SHF, as is to be expected from a wideband rig. It seems to me much better than the predecessor IC-R8500 which I owned before (but did not have it at hand for actual comparisions).
The sensitivity is less than with dedicated ham radio transceivers, at least those two I compared with. This is within expectations and also within specs. No surprise here. For real weak signal work with the IC-R8600 you would need a good antenna and good pre-amps close to the antenna.


Next up: comparison with pure SDRs on VHF/UHF/SHF, and a comparision on HF, LF, VLF.


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