OTHER PROBLEMS WITH RECEIVERS
>>> AGC Problems
Even though a radio's DR3 may be good, several of the newer radios on the market have problems with their AGC response. In the presence of repetitive loud poping noises, such as those generated by electric fences on a farm, or by thunderstorms, the AGC circuit will attack the pulse as if it were a strong signal and desensitize the receiver. It takes a second or so for the receiver to recover. By then the next pulse comes. As a result, the sensitivity of the receiver is constantly pumping, making it difficult to copy weak signals. Switching to "Fast" AGC improves this, but does not fix it. It can be very fatiging listening to SSB for longer periods of time in the AGC FAST mode.
OLDER radios did not have this problem. An old Icom IC-781 does not have this problem, nor does a Pro III. Many other older radios do not have this problem. Most new radios built since 2003 do. The only exceptions are the Elecraft K3 and FlexRadio 3000/5000.
>>> Problems with Random Spurs
Many SDR radios have this problem. This can lead to a similar performance degredation as those caused by IMD problems. An SDR radio with excellent DR3 measurements may still be a poor receiver under certain band conditions.
>>> [Receive] Audio Distortion
Some of the newer radios on the market today have awful-sounding audio. The audio distortion specification used by the ARRL for measuring this is totally useless and not representative of a radios audio quality. A closer look at these radio's in the lab has substantiated user reports. The OEMs have ignorred this problem for far too long. It must be possible to have nice clean audio coming from a 2 watt amplifier!
A radio can be an outstanding radio when used at home alone (Kevin), yet degrade significantly when used in a multi-transmitter environment, such as a Multi-Multi contest station, or a US Field Day station, where often you have one radio operating on 40m CW and another operting on 40m SSB.
Example: an SDR radio might be a great receiver with a DR3 performance higher than a K3, but when used in a Field Day environment with two transmitters operating on the same band with 70 kHz separation, that SDR radio has been seen to be 20dB worse than the K3. Part of the reason for the outstanding DR3 performance of the SDR design is that it is not a superhetrodyne radio; therefore there are no crystal roofing filters, associated mixers and amplifiers in the circuit, all of which can add IMD. At the same time, it is possibly the lack of a roofing filter that causes this SDR radio to be 20dB worse than the K3 at Field Day.
>> A WRONG PERCEPTION OF TRANSCEIVER PERFORMANCE:
It is incorrect to state that one radio is better than another, simply because it ranks higher on the DR3 list. Although DR3 is probably the most important individual specification, there are other important factors which also contribute to the radio's performance.
BEWARE OF TRANSCEIVER PERFORMANCE LISTS !!!
Different radios have different strengths and weaknesses! The challenge is to match the characteristics of a radio to your operating needs. If you do that, then you have found "your" best radio.
DO NOT EXPECT TO FIND A PERFECT RADIO.
It does not exist - not at any price!