[AMRadio] Best AM BoatanchorReceiver or AM RiceboxReceiver

Jim Candela jcandela at prodigy.net
Sun Oct 1 18:50:13 EDT 2006


 I lover your term, 'Aflak'! Pardon me, but I am going to use it..:-)

  That Sx-117 is a pretty neat receiver. I was just looking at the specifications at the following sight:


The IF selectivity at .5, 2.5 and 5 khz @ -6db is pretty tight for AM, and I bet that is why you did pretty good on 75 yesterday with 3 AM signals spaced 5 Khz apart, and a duck on either side. My Sp-600 with a 3 and 8 and 13 khz options just did not have the right bandwidth position for the conditions. There was also an Aflak at 3918 Khz running an amplifier, and was about 150 yards from my home. The SP-600 could not handle it, S-meter would go down about 1/2 what it was, and undetected SSB came right through the speaker - loud too. The R75 with preamp off, and attenuator off had no trouble with the 3918 Aflak.

In defense of that SP-600, later during the traders net the QRM subsided, and I opened the Super Pro to 8 Khz, and turned up the audio. It was clear as a bell, and the audio from those guys really came through nicely. Then the signals faded, QSB, selective fading, noise, etc. came in.

The R75 sync detector has issues, and many complaints. That said, if you use the passband tuning (say +/- 2.4 khz), with AM sync ON, it locks every time. With normal AM tunining mine seldom locks. The Kiwa mods take care of that, and several other issues.



----- Original Message ----
From: Jim Wilhite <w5jo at brightok.net>
To: Discussion of AM Radio in the Amateur Service <amradio at mailman.qth.net>
Sent: Sunday, October 1, 2006 11:33:28 AM
Subject: Re: [AMRadio] Best AM BoatanchorReceiver or AM RiceboxReceiver Discussion

Jim I listened to the same groups as you yesterday on an SX 117.  I did not 
have any trouble copying each of the groups.  While some of the aflack noise 
could be heard, it did not affect my copy that much.  I turned on the HRO 60 
with the D coil in the General Coverage mode and was able to copy very well 
with it.

I am about 500 miles North of you and was using a dipole and an inverted L 
on both receivers.  I didn't try the NC 183D but it tends to be almost as 
selective as the HRO.  I also have an R 75 and I really don't see that much 
of an improvement in reception.  I do not have all the filters in it as you 
do, but the S- AM mode does not help that much.  Also my R 75 does not have 
any modifications.

73  Jim

> Hi All,
>   Yesterday morning on 75 meters we had at least 3 AM QSO's going on
> simultaniously. It was glorious! I heard QSO's on 3880, 85, and 90. At the
> same time there were SSB groups on 3878, and 3894.
> At my QTH (central Texas) with my equipment, my SP-600 was useless. Yes I
> could use the 3Kc IF bandpass position, and tune off center to favor one
> sideband or another. As soon as the audio midrange would brighten up I'd
> hear QRM from an adjacent channel. Switching in the 8kc position resulted 
> in
> a maddening array of signals besides the one I was wanting to hear.
> Then I switched to my Icom R-75 with 3 mechanical filters that are about
> 2.4, 3.5 and 6 khz in bandwidth. I could hear all 3 QSO's Q5 in AM with 
> the
> 3.5 Khz filter, but it was no fun because the upper mids, and all highs 
> were
> gone. Then tune off 1 Khz, and much better or turn on the synchronous
> detector, offset the passband tuning 2.4 khz (or 3.5), select the 2.4 
> filter
> (or 3.5), and golly Gee! Nice sounding AM on all 3 QSO's so long as you 
> pick
> the better sideband.
> As the morning went on the QRM went away, and all we had was the traders 
> net
> on 3890. Now the SP-600 ruled until the signals started dropping from
> daytime propagation kicking in. Now I was experiencing QSB, selective
> sideband fading, and occasional impulse line noise. Switch back to the 
> R-75,
> turn on the noise blanker, and synchronous detector. Back to Q5 again!!
> This is not a tube versus solid state issue. Chuck Wa0zhh has a all tube 
> HB
> receiver that has most of the modern features, and his receiver can 
> probably
> blow the doors off my R-75. Chuck likes old style octal tubes too like the
> 6L7 in his noise blanker circuit.
> So how would a R-390 have done yesterday, or a NC-183D, Bretts HB tube
> receiver, or one of Darrel's HB tube receivers?? Just curious.
> Jim

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