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December 21st 05, 12:20 AM posted to rec.radio.shortwave

In article ,
(Mark Zenier) wrote:

In article
,
Telamon wrote:
In article ,
(Mark Zenier) wrote:

In article
,
Telamon wrote:
In article R_4of.4765$Kk7.1619@trndny05, HFguy
wrote:

The sync' detector on my R8B never growls during an extreme fade. It
stays locked. It also does DSB in addition to LSB or USB.

wrote:
The 7030 sync is a bit more versitile that that on the R8B. You can
even do DSB reception, or any mixture of LSB and USB. It's hard to
explain unless you have used one. However, the Drake gives you more
bang for the buck, especially with the weak dollar.

We did the test during the day, which is pretty difficult for
shortwave. The nice thing about the 7030 sync is it never growled
during extreme fading.

I see someone else wrote the above and responding to the comment that
the 7030+ sync is more flexible than the Drake R8B is wrong. The Drake
has selectable sideband sync and the 7030+ does not have this function.
Both radios have sync and you can adjust the passband on both but only
the Drake can sync to one sideband or the other. The result is the
blocking is better on the Drake since you can move the passband and
select the side band with the least interference.

So, what's the acoustic difference between using 1) an image reject
mixer and a broad IF filter and 2) using any sort of product detector
and a narrower IF filter?

A sideband is a sideband. If the unwanted sideband is xx dB down
from the desired signal, does it matter how it's done?

The Drake blocks better because you can sync to the side band opposite
interference and additionally you can move the bandpass control to that
same sideband. The 7030+ demodulates and syncs to both sidebands and you
can only move the passband control.

But what happens when you set the 7030+ to a narrow bandwidth, to only
cover the desired sideband? Does it sound better or worse than a R8[XYZ]
set to a wider bandwidth and using the "I/Q"/"Phased"/"Image reject"
mixer to cancel out the undesired sideband?

As I understand it, an I/Q mixer typically is good for only about 40 dB
of rejection. Is that better than the skirts on a good narrow filter?

(I could have used another 40 dB this morning. The BBC at 16:30 on
7160 was getting stepped on by some other signal. Probably something
in India on the greyline. So I used 3915 kHz, except that some of
the local ragchewers were s9+30 about 10 kHz up, and the 6 kHz filter
in my R-1000 couldn't cut it).

Moving the passband does not work as well as the side band selectable
sync.

To get away from interference the first step is moving the passband
control. If that is not enough I re-center the passband control and then
select the side band away from the interference.

I usually move the passband control for a higher tonal range on the
non-interfered with sideband.

--
Telamon
Ventura, California