9/24/08 Some Observations by Charles A Taylor, WD4INP on the Quamtum Loop QX2 v2.0 built by Radio Plus+ (as compared to my prized Space Magnet II acquired from James T. Pogue K2HAR back in 1976).
The Quamtum Loop QX2 v2.0 I acquired three days ago cost me a total of $265. An amount well invested. If you don't have one, then I suggest that you budget $25 per month to buy one. The difference between the QX2 and the SM-2 is stark. The Quamtum Loop QX2 v2.0 is most obviously superior to the Space Magnet II. The Space Magnet II has the obvious problem of a high R-F noise level. The Quamtum Loop QX2 v2.0 does not suffer from this problem. In my observation: The Quamtum Loop QX2 v2.0 is difficult to operate. The difficulty is worth the price. The R-390A/URR or the Drake R8B is obviously more difficult to operate than the Cadillac of portable receivers: The Radio Shack TRF 12-656. But either one is vastly superior to the Radio Shack TRF 12-656. Every control on the Quamtum Loop QX2 v2.0 clearly has a use. In my observation, the R-F gain control is, in fact, critical to the noise floor of your receiver. One drawback the Quamtum Loop QX2 v2.0 is hand capacity sensitivity of the tuning control! If you are willing venture inside of your Quamtum Loop, I would suggest attach- ing a pane of aluminum foil and grounding the pane. I am not willing to make this modifi- cation. The inclusion of regeneration most certainly improves the quality of the Quamtum Loop QX2 v2.0 utility. I do not yet have any observations on the current drain on a 9-V battery. However, the 12-V, D-C supply included with the Quamtum Loop QX2 v2.0 merely adds one more oppor- tunity for RFI sensitivity. I have a terribly difficult RFI situation: My wife's DirecTV modem spews forth a ter- rible spectrum of hash from 500 kHz to VHF and above. This RFI renders my prize EWE antenna nearly worthless. My wife has agreed to revert to a configuration that does not include a modem at the end of the contract period. If I did not prize my marriage more than my MW DXing hobby, then this would put a strain on our relationship. But our marriage is vastly more important than any of my hobbies! Clearly a good loop antenna is critical to my MW DXing hobby...one that I have enjoyed for the past 53 years.
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