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Re: FT-847 vs. FT-817 on 123 MHz RX

On Sun, 2003-02-23 at 07:30, Jon Ogden wrote:
> All,
> I'd like some further opinions please if anyone has any.

> On the FT-847, it's a different story.  The noise by itself (on sat or off
> sat) is around S3.  The best I could get the beacon was S6 or S7.  Turning
> off the internal preamp, drops the noise down, but then the beacon is about
> S3 or S4.  Not a very good dynamic range.  The difference in copyability of
> QSOs is tremendous.  Guys that I could easily copy on the FT-817 are not so
> easy on the FT-847.

Little background:  

AIDC 3731 with the linear dipole on the end, bbq grill dish (k5gna
package).  The DC is a 123 MHz IF and runs through the 50 or 100 ft of
RG-59, I forget which the kit comes with.  I do not have the 6 dB
attenuator in line because it fell apart on me :)

With the preamp on (I do not run it normally this way)  The beacon is
S9-10 over S9 with about a S5  noise floor.  With the preamp off  The
beacon is nominally S5, occasionally S6 or S7 when its got good squint
and not at apogee.  The noise is S1-S1.5 in this configuration.

If a station is somewhat hard to hear I'll usually try engaging the
847's attenuator, which drops the noise to S0, beacon usually drops to
S3.  And most of the time unless they're really weak it improves
readability greatly.

> I am wondering if the FT-847's front end starts to roll off at 123 MHz.  The
> FT-817 is a wider band radio and you can listen to FM broadcast, etc. with
> it.  So I am betting it has a more wide open front end.  I am wondering if
> anyone has seen similar results.  My assumption is that at 145 MHz, the
> FT-847 plays much, much better.  Anyone care to confirm this?

That's a very interesting hypothesis and I'd like to know what the
answer is from people using a 145 IF.  If its indeed the case, its will
probably be worthwhile to modify both the AIDC's I have up to 145.  I've
never accidentally tried to transmit to it yet and seem to have myself
pretty well trained on removing the coax when I'm not in front of the
847 working ao40 that its probably not an issue to move it up if it will
be a improvement.

> 73,
> Jon
> NA9D
> -------------------------------------
> Jon Ogden
> NA9D (ex: KE9NA)

Ryan Butler <rbutler@tsss.org>

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