[AMRadio] Best Boatanchor


Jim candela jcandela at prodigy.net
Fri Sep 29 23:15:59 EDT 2006


comments below... Good post Brett...Jim JKO

-----Original Message-----
From: amradio-bounces at mailman.qth.net
[mailto:amradio-bounces at mailman.qth.net]On 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 <n9wx_dan at yahoo.com>
> To: bcarling at cfl.rr.com; Discussion of AM Radio in the
> Amateur Service <amradio at mailman.qth.net>
> 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
>
>
>
>
>
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