Bob:
Thanks! Your explanation was a great help for me to understand the
history and development of the Omni VI series radios. I knew that ripple
was a design criteria by engineers but was unaware that the Inrad
filters were higher. I will search the net and find the info you
referenced in the last paragraph. I have been back operating after a 10
year absence while my son played baseball. He graduated about a year
ago. I have been slowly repairing my older TenTec qrp and cw gear to
fund my radio account.
Thanks again for your time and insight.
73
Jack WN5A
On 3/9/2013 7:32 PM, Bob McGraw - K4TAX wrote:
Well Jack, I've owned two of them and repaired several for other
folks. I'm no expert! Just a fixer with one slated to arrive on the
bench next week.
I don't have specifics about the change between the oven model which
was used in my first Omni VI Plus and the TXCO model which was my
later Omni VI Plus. The manual I have is 1st printing dated 1/97. It
shows the oven crystal. While there's nothing wrong with this
implementation, it simply requires DC power to be applied all the
time, even though the radio is off, to maintain temperature and
stability. Otherwise, it takes a few minutes for the crystal to come
up to temperature and stabilize.
I see one or more postings referencing the TCXO which is 8/06 so we
know it took place between 1997 and 2006. Otherwise, not very
specific. I sold my last Omni VI Plus along with the original
manual. Wish I'd kept a copy.
Here's a link that provides additional information.
http://tentecwiki.org/doku.php?id=563upgrade
The ripple across the top of the filters will or can make a noticeable
difference in audio response. I understand the approach toward the
INRAD filters were to move to a tighter filter which has steeper
slopes and skirts as compared to the standard filters. There seems to
be a trade-off in that with the steeper slopes, the carrier is further
down on the slope of the filter and the audio response changes and the
steeper slope design does contribute to some 3 dB to 6 dB ripple
across the top of the filter curve. I have only used stock filters in
my radios, but others have come across my bench with the INRAD filters.
As N1EU states " There are indeed differences. An early 563 and a
late 564 are very different radios in many respects aside form the
advertised feature differences. I've spent many hours of A/B
comparisons of various vintages of Omni 6/6+ from 1992 to 2001. My
conclusion is that any improvements in RX noise/birdies was subtle, if
at all audible, and that the earliest units performed as well as the
latest units." And Dave, N1LQ states, "The later 564's replaced the
crystal oven with a 2ppm TCXO on the logic board, probably the best
enhancement TT did to this radio. The crystal oven eventually "cooks
out" and will not hold frequency tolerances well. Try aligning one and
getting it to hold frequency. The TXCO fixes that problem. Later 564's
use significant amounts of SMT construction."
Hope this helps.
73
Bob, K4TAX
----- Original Message ----- From: "Jack Van Demark" <wn5a@sbcglobal.net>
To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
Sent: Saturday, March 09, 2013 6:42 PM
Subject: Re: [TenTec] Totally tricked out Omni VI+ On ebay
Bob:
You seem extremely knowledgeable on the 6+. When did they have to
switch to the TCXO's, about what year radio would have them instead
of the crystal oven?
That radio on eBay has all TenTec filters except the additional
roofing filter and circuit board.
Do you use stock TenTec filters in your radios?.
What does the excessive ripple do to the receive audio?
Thanks 73
Jack WN5A
On 3/9/2013 4:37 PM, Bob McGraw - K4TAX wrote:
Nice looking older radio. Has the crystal oven where the later
models had the TXCO. As to the INRAD filters, I find they have too
much ripple across the top to suit my taste. Your mileage may vary.
73
Bob, K4TAX
----- Original Message ----- From: "Barry N1EU" <barry.n1eu@gmail.com>
To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
Sent: Saturday, March 09, 2013 2:04 PM
Subject: Re: [TenTec] Totally tricked out Omni VI+ On ebay
Caution: if you don't want to deflate your high opinion of what an
Omni 6+
is worth, don't look at the listing ;-)
73,
Barry N1EU
On Sat, Mar 9, 2013 at 7:35 PM, Jack Van Demark
<wn5a@sbcglobal.net> wrote:
Purely an FYI!
If you haven't seen it ,there is a totally tricked out Omni VI+ on
eBay
that will go another couple of days. Wish I had more money in my
radio
account. All filter slots filled and International radio roofing
filter
kit installed.
73
Jack
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