FlexRadio 6700 - LF reception
Where I live in the San Francisco Bay Area, we have a HOT RF spectrum especially in the AM band. Using my 160m top loaded vertical as an antenna, the hotest AM radio signal is -8 dBm and there are many in the -10 to -12 dBm range.
One man's entertainment is another man's pollution; operating on 160m from my QTH benefited considerably from adding a high pass filter to cut off the energy coming from the AM band. Every radio I've operated at this QTH has had increased noise level on the low bands (80 and below) without a BCB filter.
So I was naturally curious how the FlexRadio 6700 would work in this RF environment.
Out of the box, the natural antenna choice for initial receiver testing was the 160m vertical - it captures a lot of signal and functions as a receive antenna over a wide frequency range. I connected the antenna directly to the 6700 - no in-line filters either in the direct antenna path or the RX filter loop. This is a harsh real world test for any receiver.
Tuning around the different bands with the FlexRadio 6700 was a surprise! I couldn't detect any BC band induced spurii even without the high pass filters. 160m had its fair share of QRM from local noise sources - I know what causes some of them (the ones on my own QTH) and others I have a fair idea (the variable speed pool pump in a new construction about a half mile away for example). But that was it!
Another interesting test for any receiver is to see how its LF performance functions. Although we haven't got low frequency allocations at 137 KHz or 497 KHz yet, hopefully we will in the not too distant future. I was curious to see how the 6700 would perform at those lower frequencies.
At LF, my 160m vertical is a very short antenna! Despite that, I've been able to receive a lot of LF stations especially aviation non-directional beacons (NDB). Most of these beacons serve as navigation aids for instrument approaches into airports. Many of the US NDBs are being de-commissioned as GPS has rendered them obsolete. But you can still hear multiple beacons in the LF spectrum from 200 to 400 KHz.
All the beacons have a callsign sent in CW or MCW and I quickly found a good directory mapping frequency, callsign etc to location compiled by William Hepburn of the LWCA - you can find the directory here.
Not withstanding the inefficient antenna I can hear beacons all over the Western states (Arizona, Utah, California, Idaha, Oregon, Washington - all logged) as well as many up in Canada. I used Google maps to find some of the locations like NDB ZP at Sandspit, BC which I can regularly copy.
Here's a capture of SmartSDR tuned to WL (Williams Lake, BC) which Industry Canada shows on 0.385204 MHz running 500 watts into a 0.5 dBi antenna at 6 meters above the ground. BTW, a couple of notes about this capture...
- You can see that the radio is in WIDE mode - no bandpass filters selected in the receiver.
- The S meter calibration is accurate but ignore the level scale on the panadaptor as its not yet calibrated.
The clip is short - you can only listen to a beacon id so many times!
On the ham bands, the 6700 receiver truly shines! As I've said before, the radio sounds very clear and its strong signal performance is excellent. Even with the SteppIR as my primary HF antenna, I can monitor different bands to see if there is activity by using multiple slice receivers - of course a tribander or multi-band HF yagi would allow monitoring with optimum signal levels but wouldn't be as cosmetically friendly!
I'm looking forward to using the 6700 in a contest and also improving my low band receive antennas - the 160m vertical is noisy and this summer I plan to build a receive only 4 square. That should help my 160m and 80m receiving conditions a lot!