comments below... Good post Brett...Jim JKO -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Brett gazdzinski Sent: Friday, September 29, 2006 8:31 PM To: 'Jim Candela'; 'Discussion of AM Radio in the Amateur Service' Subject: RE: [AMRadio] Best Boatanchor
I have used some of the best of the modern (IC chip) ham and swl gear for receivers and I think it all sucks big time. Jim says, Got any examples? I have a Yaesu FT-757 transceiver, and the receiver portion on that is really poor. I like to hear a quiet receiver at full gain, and then connect the antenna to be blasted from normal band noise. With the 757 it gets quieter when you connect the antenna!!! My quietest receiver is the AR-88. You hear almost nothing with the antenna disconnected. Plug in the antenna even on 10m when the band is dead, and you still hear atmospherics, car ignitions, tec. With My Icom R-75 I don't hear much on 10M unless the band is OPEN. On 160-20m the sensitivity of the R75 is adaquite. Jim says, I have a SSB Ham about 150 yards from me that runs on 3918Khz with an amplifier. He is clean. With my SP-600 tuned to 3880, He de-senses my Hammerlund, and the S-meter goes way down when I am listening to AM, and the audio gets real distorted. With the Icom R75, all I hear is his T/R relay clicks, and the Icom untuned front end has the dynamic range without narrow band selectivity at RF to accept his signal, and not overload. The Icom will act up however if I am using the noise blanker when adjacent signals are real strong. Its noisy and distorted, look at the specs, 1 watt at 10% distortion, and that is just the audio amp! Jim says, The last I looked, a 6V6 or 6K6 single ended tube output is rated at a few watts at 10% or so THD. As for the Icom, there is a record output jack in the back so you can use an external amplifier. One of the Kiwa mods move the audio bandpass from ~ 3khz to about 4.5 Khz by changing R-C values in a multi-pole active LPF. Distortion is very low, and the standard AM detector is very good. For the old gear, it depends on what you want. Some of the old stuff would go broad as a barn door, with push pull direct coupled 6L6 output audio tubes, and sounds fantastic! Jim says, Direct coupled PP 6L6's? Both my AR-88 and SP-600 use a single ended audio output tube, and I've added negative feedback. With the RCA I also run the cathode through the 600 ohm winding, somewhat copying the Macintosh circuit. In both cases I get 2-3 watts of fantastic audio. The problem however is the RF selectivity in the presence of adjacent channel interference cannot match a receiver with a well shaped mechanical filter bandpass. The dynamic range of my tube stuff isn't at the level of the Icom either, so I sometimes have to back down the RF gain (SP-600). Operating 3880 AM with the big guns on 3878 LSB is really tough with my RCA or Hammerlund. With the Icom using Synchronous detected AM with 3khz bandpass selected, looking at the AM USB only with the passband tuning, the AM reception is almost perfect. I don't hear them 3878 LSB operators at all even though they might be S9+40 on peaks, and the AM station on 3880 might only be S7. You cant tell what frequency you are listening to, but it sounds great. Jim says, There are digital frequency readout adapters for tube receivers that are programmable for the IF offset(s). The NC300-303 are good, the R390 is good, the SX17 or SX28 are good, the Scott SLRM is very good, with its magic eye tube as an S meter. The boatanchor receivers all have their good and bad points, but most are better then the noisy distorted modern solid state crap. Jim says, You are correct about most solid state communication receivers made up through the 1980's, After that we got devices with > 100db dynamic range that can without a lot of selectivity listen to a whole band, and not overload. Today there is anything from crap to state of the art with solid state devices. The Icom R75 is a very good 'bang for the buck' receiver comparable to the Drake R8 at a fraction of the price. I don't know about an SWL receiver, but for a HAM receiver, the R390/R390a was the best one I had before the homebrew. Its noisy and does not like to band hop, but with outboard audio, it sounds and works well on AM. Jim says, I never had one. I'd like to play with one for sure. I got tired of the commercial crap and home brewed a few tube type HI FI AM receivers, and they work so well I sold off all the other receivers. Jim says, I followed your receiver posts a few years ago with great interest. You are a very good designer, and AM ham. I bet that receiver you made is one heck of a fine receiver. I wish I lived closer.. My favorite vintage receivers were the R390/390a, the SX 17, the Scott SLRM, and the NC300/303. The R390 and NC300 need outboard audio to sound good, the others you had no good frequency readout. The NC300/303 are still reasonable in price. The Collins S line receivers have promise, with outboard audio, and good AM detector, and a good IF filter, the 75s1 might be a good receiver as they are reasonable in price, accurate and stable, and a small light box. They look cool also! Brett N2DTS > Daniel, > > I have a suggestion that you might ponder. Save the boat > anchor for the transmitter, something like a Johnson Ranger. > For the receiver consider a more modern Icom R-75 general > coverage receiver. I own one of these, and with appropriate > filters, these are absolutely excellent on AM, and are all > mode as well. The Kiwa folks have a whole array of > modifications too that enhance overal reception with an > emphasis on SW AM broadcast reception. You might get a used > R-75 for $350, and add another hundred or so later for the Kiwa mods. > > I also have an RCA AR-88, and Hammerlund SP-600 receiver. > These are very nice, but since getting the Icom, I put the > RCA on the shelf, and I only on occasion turn on the > Super-Pro. The mechanical filters in the ICOM, offset > passband tuning, synchronous AM detector, Noise Blanker, and > DSP all stand out over my two boatanchors. That said, the > super pro has superior audio, and sensitivity. When the band > is noisy, and crowded, I use the Icom. The RCA is sort of in > between, but it too has good qualities (except it weighs a > hundred pounds!). > > Regards, > Jim > WD5JKO > > ----- Original Message ---- > From: Daniel Hileman <[EMAIL PROTECTED]> > To: [EMAIL PROTECTED]; Discussion of AM Radio in the > Amateur Service <[email protected]> > Sent: Friday, September 29, 2006 10:48:22 AM > Subject: Re: [AMRadio] Best Boatanchor > > > Hi Guys, > > Thanks for all the suggestions...there are LOTS of > favorites for sure. I guess I have a little thinking and > investigating to do. Thanks for all the input...now it's time > to start the homework! > > Thanks and 73, > Daniel N9WX > > > > > > ______________________________________________________________ > AMRadio mailing list > List Home: http://mailman.qth.net/mailman/listinfo/amradio > Partner Website: http://www.amfone.net > Help: http://mailman.qth.net/mmfaq.html > Post: mailto:[email protected] > ______________________________________________________________ AMRadio mailing list List Home: http://mailman.qth.net/mailman/listinfo/amradio Partner Website: http://www.amfone.net Help: http://mailman.qth.net/mmfaq.html Post: mailto:[email protected] -- No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.1.405 / Virus Database: 268.12.9/456 - Release Date: 9/25/2006 -- No virus found in this outgoing message. Checked by AVG Free Edition. 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