Hi Ethan,
Welcome to the DEMI documentation world.  It's one that I never can
seem to find the exact schematic to agree with what I am working on as it
seems their documentation never kept in step with the product version.  Tom
N8ZM would say contact them and see if they can get you close.  They have
asked me to send a picture before but even then it wasn't exactly what I
was
working on.  Generally yes the high drive level option does give you a
common IF as well, so yes you should skip that and go directly to the RX
and
TX inputs and of course then a low power IF source will be needed less than
one watt.  There should be a variable pot to allow some adjustment to the
drive level if you can't adjust that and I would set that up to start
with.

As for heat does this one have a heat sink on it and if so generally we
haven't needed them running 20 watts or so.  Now running FT8 it might not
be
a bad idea but I would try it and hand test how hot that gets it.  The fan
actually might help with frequency drift.  I would just experiment and see.
We have one of the later model DEMI's (white box) on the hill station which
does come with the heat sink and fan both I think but the old old ones in
diecast housings didn't even have a heat sink were later ones did.

Randy WB8ART

-----Original Message-----
From: Ethan Miller K8GU via mvus-list [mailto:mvus-list@lists.febo.com]
Sent: Tuesday, January 4, 2022 10:11 PM
To: VHF Contesting; Midwest VHF/UHF Society Mailing List
Cc: Ethan Miller K8GU
Subject: [mvus-list] DEMI 222 help

All,

I acquired an old DEMI 222-28 transverter from the K8CC estate last summer
and I'd like to get it rolling for the spring/summer contests (I have to
beam through "Mount Kettering" to get to the center of 222 Tuesday nights
from my home QTH and biggest amp I have for 222 is a 60-watt Larcan
pre-driver).

This unit has the M67712 hybrid as the PA and does not seem to match any of
the legacy schematics found on (the current) DEMI web site.  It's wired for
common-IF with what looks like an attenuator for high drive power.  Do I
need to know anything special about converting it to low-drive split-IF to
work with my K3 and K2 (and TS-930S)?  Or can I just remove the
attenuator/switching board and run coax straight from the rear panel
connectors to the RXIF and TXIF pads on the board?

Also, any experience or opinions about using the M67712-based transverter
on digital modes?  Muffin fan?  Low power?  Both?  I've been off the bands
above 6m the past couple of years since I moved from FM19 to EM79; but, if
my experience on 6m and the kvetching on the reflectors are any indication,
I'll need to spend some time on FT8.  I'm sure the Larcan pre-driver will
be fine at high duty cycle.

Thanks/73,

--Ethan, K8GU.

--
http://www.k8gu.com/
Repair.  Re-use.  Re-purpose.  Recycle.

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Hi Ethan,
Welcome to the DEMI documentation world.  It's one that I never can
seem to find the exact schematic to agree with what I am working on as it
seems their documentation never kept in step with the product version.  Tom
N8ZM would say contact them and see if they can get you close.  They have
asked me to send a picture before but even then it wasn't exactly what I
was
working on.  Generally yes the high drive level option does give you a
common IF as well, so yes you should skip that and go directly to the RX
and
TX inputs and of course then a low power IF source will be needed less than
one watt.  There should be a variable pot to allow some adjustment to the
drive level if you can't adjust that and I would set that up to start
with.

As for heat does this one have a heat sink on it and if so generally we
haven't needed them running 20 watts or so.  Now running FT8 it might not
be
a bad idea but I would try it and hand test how hot that gets it.  The fan
actually might help with frequency drift.  I would just experiment and see.
We have one of the later model DEMI's (white box) on the hill station which
does come with the heat sink and fan both I think but the old old ones in
diecast housings didn't even have a heat sink were later ones did.

Randy WB8ART

-----Original Message-----
From: Ethan Miller K8GU via mvus-list [mailto:mvus-list@lists.febo.com]
Sent: Tuesday, January 4, 2022 10:11 PM
To: VHF Contesting; Midwest VHF/UHF Society Mailing List
Cc: Ethan Miller K8GU
Subject: [mvus-list] DEMI 222 help

All,

I acquired an old DEMI 222-28 transverter from the K8CC estate last summer
and I'd like to get it rolling for the spring/summer contests (I have to
beam through "Mount Kettering" to get to the center of 222 Tuesday nights
from my home QTH and biggest amp I have for 222 is a 60-watt Larcan
pre-driver).

This unit has the M67712 hybrid as the PA and does not seem to match any of
the legacy schematics found on (the current) DEMI web site.  It's wired for
common-IF with what looks like an attenuator for high drive power.  Do I
need to know anything special about converting it to low-drive split-IF to
work with my K3 and K2 (and TS-930S)?  Or can I just remove the
attenuator/switching board and run coax straight from the rear panel
connectors to the RXIF and TXIF pads on the board?

Also, any experience or opinions about using the M67712-based transverter
on digital modes?  Muffin fan?  Low power?  Both?  I've been off the bands
above 6m the past couple of years since I moved from FM19 to EM79; but, if
my experience on 6m and the kvetching on the reflectors are any indication,
I'll need to spend some time on FT8.  I'm sure the Larcan pre-driver will
be fine at high duty cycle.

Thanks/73,

--Ethan, K8GU.

--
http://www.k8gu.com/
Repair.  Re-use.  Re-purpose.  Recycle.

mvus-list mailing list -- mvus-list@lists.febo.com
To unsubscribe send an email to mvus-list-leave@lists.febo.com

mvus-list mailing list -- mvus-list@lists.febo.com
To unsubscribe send an email to mvus-list-leave@lists.febo.com