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![]() 4nradio wrote: "Eric F. Richards" wrote in message ... "Brian Denley" wrote: Guy Atkins wrote: I've had a Ten-Tec RX340 in the shack for a month, and it performed significantly worse on tough DX than my modded R-75 and the RA6790GM I used to have. ------------------------------------------- Any RX-340 that gets outperformed by a R75 needs to be taken to the shop. I would tend to agree, unless his definition of "tough DX" is extremely narrow. Hi Eric, I should clarify that I had TWO RX-340s on loan, and both performed equally sub-par at home. On DXpeditions away from strong RF sources, they are fine receivers. I'll quote from my reply today to Larry Magne, who heard through the grapevine that I'd done some A-B-C receiver comparisons involving a RX-340 and wanted more information before IBS plunks down $4,000 for another sample to test. Sorry for the length of this post, but it addresses the questions brought up: ----------------------------------------------------------------------- "Thanks for the note and questions about the RX-340. I do not own a RX-340, but have DXed occasionally with two different ones at coastal DXpeditions, and this fall I had a close friend's RX-340 on loan for an entire month. I also had another friend's RX-340 here for a couple of weeks. I used both RX-340s extensively in October and November, along side my modified R-75 and also a Racal RA6790GM (with narrower, 10-kHz roofing filters). Each radio was fed with signals from my Beverage antennas through a Mini-Circuits splitter. Note that I didn't have both RX-340s here at the same time; one followed the other. My impression of the Ten-Tecs at DXpeditions has always been very good. However, at our group's usual DXpedition site of Grayland, WA, there are no nearby strong RF sources to cause problems. At home it's a different matter, unfortunately. My permanent Beverages are aimed at my favorite Asian and subcontinental targets, but the wires are pointed "down the barrel" toward Seattle/Tacoma area powerhouses on mediumwave (I live to the east of Tacoma, and my targets--and pests--are generally to the west). I have a number of locals that are in the S-9 + 50db range on my receivers and a few at S-9 + 65db. Despite the RF alley I manage to log trans-Pacific MW DX from home; Japan, Korea, and China stations were in abundance this past fall! On the tropical bands I switch in a Kiwa BCB filter + Extension Filter to ease the load on the front ends of receivers. Despite the two highpass filters inline, the RX-340s struggled to hear weak DX on the tropical bands and above. Both my R-75 and RA6790GM performed well and practically identical under the same conditions. I initially believed the problem was RF blocking of the RX-340s' front end, but Dallas Lankford told me he thinks it's a matter of the RX-340 circuitry reducing the gain in order to "protect" the DSP AGC loop. When the DX was audible on the RX-340s, it was always weaker and with poorer intelligibility than the R-75 and RA6790GM. I did numerous tests throughout the month, and never did the Ten-Tec equal the performance of the other receivers. They were also the worst performers when the trans-Pacific MW DX was coming in. I'm not aware of any production changes that would affect the RX-340 in this way. Attached are two short MP3 recordings from my files, demonstrating the audio from an RX-340 and my R-75. The station is AIR Bangalore on 9425, shortly after it rose above threshold level and began to be slightly readable. The antenna was my 700 ft. Northwest Beverage, fed equally through the Mini-Circuits splitter. As you'll note, there's just noise from the Ten-Tec's MP3 recording. I have another set of recordings from 3320 kHz (RX-340, R-75 and RA6790GM), and the results are similar. By the way, Ten-Tec "guru" Carl Moreschi, N4PY, developed a mod for the front end of the radio that I installed in my friends' RX-340s. It's a 4 kHz Kiwa filter module that can be switched in and out of the 2nd Mixer/IF Board via a relay. He claims it provides over 100 db dynamic range for signals between 5 and 10 kHz removed from a strong signal. I installed the mod in the two RX-340s that I had on loan. It worked very well--at times-- on mediumwave to restore sensitivity close to a powerhouse. Unfortunately there was an overall attenuation that N4PY and I could never figure out, and after much head-scratching and experimenting, my friends and I gave up on the mod. They didn't want to sacrifice any performance of their RX-340s in the low-noise, low-RF DXpedition environments we enjoy so much. I was as surprised as anyone by the lackluster showing of these $4K receivers! My R-75 has numerous mods including a narrower roofing filter, but I didn't think it could surpass (or equal) a RX-340 under equal, but difficult RF alley conditions. I thought the Racal with its twin roofing filters mod *might* give the RX-340 a challenge, but I never expected it to consistently better the Ten-Tec. I'll note that every "serious" communications receiver used by the Grayland participants has performed very similar to the others, time and time again. Our core group of DXers has travelled to the WA coast since 1989 for 2-3 times per year, and we've had ample opportunity to compare our receivers. Particularly on the foreign mediumwave stations, you'd be hard pressed to tell any differences in weak DX readability between a $500 R-75, a $1500 R8B, or a $4000 RX-340! It wasn't until I had a chance to use the RX-340s in my suburban area that I discovered the surprising differences. As a side note, I recently sold my Racal and bought an ICOM IC-756Pro transceiver through Ebay for $1500 and I am extremely pleased with it. I wanted to have an all-DSP communications receiver at a more modest price than the RX-340, but didn't like IP3 & close-in dynamic range numbers I'd been reading for the Winradio G3 series (which I otherwise liked a lot). The 756Pro *consistently* outperforms my modded R-75 at home, and I look forward to getting them to Grayland for comparisons in that optimum environment. The 24-bit DSP and AGC within the DSP loop evidently contributes higly to the performance of ICOM's 756Pro series. I know of three other DXers who have now bought 756ProII and 756ProIII models based largely on my findings and posted reviews. They are also tropical band and foreign mediumwave DXers. At a price of ~$1700 used, or $2100 new, the IC-756ProII is quite a receiver, even for receive-only DX. You gotta love that spectrum display, too! My apologies for the lengthy reply, Larry, but I felt it best to give you a full backgrounder to my disappointing experience with the two RX-340s I had on loan. " --------------------------------------------------------------------------- If anyone wants to listen to the MP3 samples referred to above, email me at (remove the NOSPAM) and I'll send you the MP3's as attachments. I'm not out to bash the RX-340, as I better things to do, such as DXing! If anyone's interested in a bit of my background that briefly describes my hobby qualifications (ie., I'm not a newcomer at DXing or evaluating receivers through hands-on use), please see this bio at dxing.info: http://www.dxing.info/about/dxers/atkins.dx Guy Atkins Puyallup, WA USA I had a 'loan' of an RX340 some time back, I used it for several weeks and it was returned. Nice enough receiver, but certainly not worth the $4K price tag as I've stated here several times already. dxAce Michigan USA |
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