Re: The Southern CCrane SWP Slider
Thanks for your detailed testing of the SWP Slider's resistance to overload, which is much appreciated.
It's true that the stock C.Crane SWP model has somewhat of a problem with image frequencies, but the 7.5" Slider loopstick acts as a tuned circuit to filter out these nuisance signals (when the coil is peaked on the frequency that has the image). In my local environment the 1450-KSUH pest typically puts in a strong image on 540 kHz with 455 kHz IF radios (SWP, E100, etc.) but the Slider loopstick can reduce the strength of the image down to a very low level. The additional tuned circuit provided by an external tuned passive loop can finish the job by making all images disappear completely. In agreement with your findings, I've been very happy with the SWP Slider's resistance to overload, which is of extreme importance when using a high-gain antenna like the 9' PVC box loop.
In a message dated 10/19/2010 4:12:14 P.M. Pacific Daylight Time, w4dst@... writes:
On 10/19/2010 3:02 AM, D1028Gary@... wrote:
>The SWP Slider model has outstanding resistance to overload, which makes it ideal for use with the 9' loop. In this respect, it's probably a shade more impressive than the Si4734 models. The >fact that the SWP Slider has its own tunable loopstick contributes to this stability, and when the tunable Slider loopstick is combined with the 9' loop's tuning capacitor, the ultimate selectivity of >the system is probably close to optimum in the Ultralight class.Even with a large ferrite bar antenna, the SWP exhibits much better front end resistance to high RF levels than the PL-310, at least in my tests it does. But it should be noted this is an apples to oranges comparison since the SWP is a more "traditional" radio with a 455kHz IF and analog style front end, as opposed to the digital circuitry of the Si4734 based radios. The digital filters in the Si4734 radios are outstanding for my east coast DXing, but the ability to tune the Slider, along with the SWP features which the Tecsun radios lack, makes the SWP Slider my MW radio of choice. There are features in the Tecsuns that I wish were in the SWP, like the ability to keep the back light on and of course the signal strength readout. The Tecsuns need a 10/9kHz UP/DOWN feature like the SWP. The G8 has it and I wish my '310 and '380 had that feature.
I recently tested the SWP Slider against a stock PL-310 at a site about a 1/4 mile from my local WHKP 1450 antenna. I may have failed to post my findings and if so here they are again although the signal strength readings from the PL-310 are lost. The PL-310 overloaded and no stations were heard from 1390 up through 1560 kHz except for an image of 1450 which appeared at 1540. I had noted this image in a previous trip to the transmitter site. The Slider could log 1440kHz in Greenville, SC,50 miles away and 1400kHz in Waynesville, NC 35 miles away both with good audio, neither of which the PL-310 could hear at all. There was even a trace of audio on the Slider from 1460 WHBK in Marshall, NC, about 45 miles to the north so there was very little desensitizing of the front end on the SWP even with the Slider. There was also no image at 1540 on the SWP , I wasn't expecting one, although one did show up on 540, which is 1450 minus 2X the SWP IF of 455kHz. This is quite common for single conversion 455kHz IF frequency receivers although on the SWP it was at a much lower level than many other receivers. At my mother-in-law's house 3 miles away, there was no trace of images on either radio at their respective image frequencies. My old Sangean ATS-909 had a very strong image of 1450 WHKP on 550 at her house. The Sangean IF was/is 450kHz rather than the more common 455kHz. I would have expected the SWP with that big ferrite bar to have had some serious problems with overload and imaging but that just wasn't the case even as close as I was to the antenna tower.
We are planning a trip to the SC coast in the next couple of weeks and I will post my loggings to the list. That is a good place for TA, Cuban, Caribbean, and sometimes South American DX. The problem I have is finding time to DX since this is mine and my wife's get-away vacation and playing with the radio is not one of her top priorities.