Posted by
wc1m on
Jul 25, 2009; 5:30pm
URL: http://elecraft.85.s1.nabble.com/K3-160M-Diversity-Users-tp3322951p3326207.html
My experience pretty-much aligns with Bill's. I started out with matched
pairs of 5-pole 500 Hz and 5-pole 200 Hz filters. The 500/200 combination
makes a little more sense than the 400/250 combination because there's more
difference between the filter widths.
Like Bill, I rarely use the 200 Hz filters. Most of my use is contesting. If
you spend too much time with BW cranked down to 200 Hz or less, you're going
to miss a lot of callers. I only use narrow BW when someone plops down very
close to my frequency when I'm in the middle of a QSO. That said, the narrow
BW saves me every now and then, which for me is worth the cost.
I was fairly satisfied with the 5-pole 500 Hz filters, but was sometimes
bothered by thumping and clicking from loud stations (S9 and higher) just
above my passband. This is likely caused by the hardware AGC activating at
somewhat too low a level. Quite a while ago there was a fix to the RF board
to raise the threshold, but some of us think it's still too low.
At any rate, though the theory says that roofing filters aren't responsible
for the ultimate selectivity (the DSP does that), I found that they do make
a difference in the above situation. Switching off the 500 Hz filters and
using the 200 Hz filters produced audibly less interference, most likely by
providing greater attenuation at the hardware AGC stage. That induced me to
replace the 5-pole 500 Hz filters with 8-pole 400 Hz filters.
The result was a minimal improvement, not easily detected by testing. The
real test will come this fall when I'm squeezed into 40m or 20m with
zillions of loud stations on either side.
All that said, Bill is correct that, with the matching fee, the price
difference between 5-pole and 8-pole filters is small enough that it makes
sense to get the 8-pole filters. I should note that the 8-pole filters are
not necessarily perfectly centered, but they're close enough that you
probably won't need to use any offset for diversity.
As far as the 200 Hz vs 250 Hz filters go, if you want to have them in
reserve for those really tough QRM situations, I would get the 5-pole 200 Hz
filters. Elecraft says they're narrower than the 250 Hz filters all the way
down. Also, there's more BW difference between the 200s and the 400s/500s.
I agree completely with Bill on the merits of diversity: with the right
antennas, it's amazing.
73, Dick WC1M
> -----Original Message-----
> From: Bill W4ZV [mailto:
[hidden email]]
> Sent: Friday, July 24, 2009 10:27 PM
> To:
[hidden email]
> Subject: Re: [Elecraft] K3 160M Diversity Users
>
>
> W4UM wrote:
>
> > What are your recommendation if I were to get only
> one pair of filters?
>
> I would go with either the 500 or 400 8-poles.
>
> > Is there any real value to getting a pair of narrow
> (200Hz or 250Hz) filters as well as a pair of the wider (400Hz or 500Hz)
CW
> filters, or am I just wasting money?
>
> I have a 200 Hz in my Main in addition to 500 Hz 8-poles in Main and Sub.
> If you contest or are in huge simplex pileups, there are definitely times
> when the 200 Hz may be useful. For some reason I don't understand, I have
> no offset warbling when setting WIDTH to 200 (which enables the 200 Hz in
> Main and 500 Hz in Sub). Most of the time when listening to weak signals,
I
> use 350-500 Hz WIDTH so a pair of 500 Hz filters is fine excluding the
> extreme cases of simplex pileups or a strong station nearby (e.g. the CQ
160
> CW contest).
>
> > Is there a noticeable difference between the 5-pole and 8-pole filters?
>
> I used 5-pole 500s in my first K3 and have not noticed a significant
> difference with the 8-poles, but I've not compared them simultaneously.
As
> you stated, there's little cost difference (after the matching charge) so
I
> went with the 8-pole 500 Hz when it became available. I personally prefer
a
> slightly wider BW than the 400 Hz allows but that's another option some
> choose.
>
> You'll love diversity on 160 and 80, especially if you have good RX
> antennas. I use my TX antenna (similar to a 4-square) in one RX and
> Beverages in the other, and I use diversity 99% of the time on the low
> bands. I would never own any rig without diversity now that I've used it.
>
> 73, Bill W4ZV
> --
> View this message in context:
http://n2.nabble.com/K3-160M-Diversity-Users-> tp3322951p3323855.html
> Sent from the Elecraft mailing list archive at Nabble.com.
______________________________________________________________
Elecraft mailing list
Home:
http://mailman.qth.net/mailman/listinfo/elecraftHelp:
http://mailman.qth.net/mmfaq.htmPost: mailto:
[hidden email]
This list hosted by:
http://www.qsl.netPlease help support this email list:
http://www.qsl.net/donate.html