What Radio or Rig Do I Need



If you ask owners of the same radios how the radio works you can get a wide range of answers. We often find owners don't notice a radio performs poorly compared to other radios even when the radio has known major defects or shortcomings.  This is why we have to be very careful asking opinions about radios.

Why the Difference in Opinion?  

Sometimes we become emotionally attached to our toys. After all, we invest time and money in our hobby. We have a right to enjoy what we worked for. Sometimes the attachment or emotions greatly affect our opinions.

I remember the first brand new radio I ever bought. After years of home brewing or buying second or third hand gear I finally was in a position where I could afford a brand new high end radio. I carefully asked all the right questions and heard all the answers I was looking for. I purchased a radio people I trusted really liked, and I took delivery of my very first brand new radio. It was an expensive radio but I finally was able to buy my first top of the line new radio.

I loved the large digital readout. The receiver sounded great. People gave me glowing reports; they all said the transmitted audio sounded wonderful. Then the second or third day came along.....

After a few days of SSB ragchews and barefoot CW contacts I finally listened for some weak CW DX. My local noise floor is way down near S1, even on 160 meters, so DXing should be a real pleasure with such a fancy radio. I heard a weak but easily readable signal in the area where DX normally hangs out, i expected it to be European DX. I was shocked to hear it was VE1ZZ. I wondered why Jack was only S-3 instead of his normal S-9 + signal. I tuned up the band a little higher in frequency, and there was Jack VE1ZZ again but this time his normal S-9 signal strength! Puzzled by this and wondering of Jack had a problem, I did my customary crosscheck. I used a totally different type of radio to look for the same spurious signal. The second weak signal from Jack wasn't there at all on my old IC-751A! It wasn't there on an old R4C Drake either. Obviously the new expensive receiver had some spurious responses, even on a signal from a few thousand miles away!

I tried transmitting using that rig with my full-power amplifier. It was a single 8877 with 4000 volts on the anode. This required reducing the power output of my 150 watt radio to about 50 watts. I reduced the power, loaded up, and was all set to transmit. As soon as I touched the key the amplifier tripped right off. It gave me a "grid current overload" fault. How could that be? I loaded up to only 25mA of grid current.

I advanced the loading control on the amplifier and hit the key again. Now the amplifier dumped because of an SWR fault.

Out to the shop I went, new radio in my arms. I quickly discovered the receiver would actually hear signals on an unselected VFO when the unselected VFO and active VFO were close in frequency! While this spurious response was 50 or more dB down (depending on VFO spacing), it was enough to cause spurious signal responses on a VE1 a few thousand miles away on 160 meters! This was not good. Making matters even worse, the transmitter had the same spurious response. I could generate, with the right VFO spacing, weak spurious signals spaced at the VFO separation of and also on both VFO frequencies.

I looked at the transmitter power and my mood suddenly worsened. I discovered the transmitter, on a good peak detecting meter I used for pulsed transmitter measurements, had a leading edge power spike of 250 watts or more! Worse yet it had this same power spike when the power control was reduced to 50 watts. No wonder it was tripping the very fast fault detection circuits in my amplifier.

A call to the manufacturer revealed they actually knew about these issues. They said I was stuck with the power spike, but the receiver and transmitter spurious responses were caused by leakage through a solid state switch that selected or deselected the unused VCO's. They could cure the spurious signal problems by making a factory modification to completely turn off unused VCO's (the front panel calls them VFO's) if I was willing to give up QSK operation.

Why didn't others notice the problems?

If we have a noisy location, work only strong signals on SSB, have small antennas, and run low power almost any radio will be good enough.
The better our location, the better our antennas, the more power we run, the narrower the selectivity we use, and the more we operate congested bands the more important radio performance becomes. When I was in strong SSB ragchews, when I wasn't working split frequency, and when I didn't have the low-drive amplifier with fast protection circuits on, everything looked great. I would have told anyone who asked to buy that radio, just as my friends told me.

My friends mostly work SSB and don't have particularly quiet locations or big antennas, and those were the people I relied on for advice. If I never worked weak signal DX from a quiet location, never operated close to other people, didn't work much CW, and didn't have a fast protection system in my amplifier I probably would not have noticed the serious flaws in that $3000 dollar radio. If i only worked SSB i would have thought anyone finding fault with that radio was crazy.

What's important to you?

As humans with emotions, we all make some pretty stupid subjective claims from time to time. I've seen people claim an $8000 radio with a close-spaced signal dynamic range defect is bothered by other signals because it "hears better, and so it hears the defective signals where other lesser receivers will not".  Others will claim they changed receivers and suddenly HF noise was greatly reduced. Unfortunately these statements are actual technical rubbish. 

Virtually any radio today has plenty of sensitivity. Virtually every radio made in the last 20-30 years will "hear" way down into ambient noise at the quietest location when on a reasonable antenna, even when the antenna is just an ordinary old dipole. For many years internal receiver noise has not set the limit of hearing weak signals, the external noise sets the weak signal limit. For the same general filter selectivity on a clear band, virtually all radios produce a signal-to-noise ratio determined solely by the signal-to-noise ratio at the antenna.

What sometimes fools us is AGC slope at low levels or the overall receiver gain. If one receiver has a bit less sensitivity than another and we listen to fair signals, the lower gain receiver (or a receiver with less AGC loop gain) will provide an illusion that background noise has decreased. This illusion occurs  because receiver gain between signal amplitude peaks is not nearly so high. The receiver does not reject or remove noise, the background noise between signal peaks just doesn't pump up so high. Years ago receivers had an RF gain control that was used just for this purpose, to reduce sensitivity and make a signal sound clearer. Today the receiver RF gain control virtually NEVER controls the RF gain!! In the modern rig the RF gain control is generally a mislabeled or incorrectly named IF gain control.  Today, in nearly all cases, the only way to reduce RF gain is to turn off the receiver's preamp or add an attenuator pad.

What is the difference between rigs?

Other than bells and whistles 99% of us never use and transmitter power output, the only consistent benchmarks are the bandwidth performance of both the receiver and the transmitter.

When we buy a less expensive "does everything radio", like a compact portable or mobile rig, we generally get the worse end of modern transmitter and receiver bandwidth performance range. Strong close-frequency stations, even when they have no transmitter defects, will bother the receiver. The transmitter will also bother others much more than necessary when we are strong.

Filtering is also important.  A few radios totally omit conventional analog IF filters, depending exclusively on DSP filters. "DSP processing only" receivers, whether $800 or $8000 rigs, almost always provide significantly poorer close-spaced performance than similar radios using conventional crystal or mechanical IF filters. The best receivers combine very narrow selectable roofing filters tailored for each mode with a good DSP or standard filtered IF and detector stages. The Ten-Tec Orion or Elecraft K3 have two of the very best receivers, far better than much more expensive radios.

It's important to keep in mind if we never operate close to other strong signals, if we have high local noise, if we use small antennas and/or low power, and if we operate wide bandwidth modes we aren't nearly as likely to appreciate good quality.

ARRL reviews have now improved. The ARRL now tests and reports performance at closer spacing. It is worth looking at ARRL reviews, especially at close-spaced IM3 dynamic range and transmitter IM distortion. ARRL numbers are more useful now, although review text sometimes has the same unreliable emotional hyperbole we find on the air.

Also look at the following links on this site for  receivers  and transmitters.


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