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K3s and DEMI transverter

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W8JH

K3s and DEMI transverter

I am looking to add the DEMI (Q5) transverter to my K3s and have no
experience with transverters other than the internal one in my KX3. In the
future, I may wish to progress to 2m EME as well.

Here are some choices I need to make and I would appreciate any advice:

Common IF vs Split IF. I'm thinking split IF with a K3s?

Common RF or Split RF. Common RF for one antenna connection?

IF drive level of -20 to 0dBm vs 0dBm to +20dBm. I think the K3s
transverter output is 0dBm so I'm not sure what to think here.

PTT polarity low instead of high I'm thinking.

High stability Local Oscillator vs. standard.

I could get a custom IF and I think there is some slight advantage to a
14mHz custom but I'm guessing the 28mHz standard IF is good enough?

Thanks in advance for any advice or references.

-----
73,

Joe, W8JH

K3s, KPA 500, KAT 500 and KX3 happy user.
--
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73,

Joe, W8JH

K3s, KPA 500, KAT 500 and KX3 happy user.

Mooneer Salem

Re: K3s and DEMI transverter

Hi Joe,

From what I've been able to tell, for what most people use transverters for
(SSB/CW on the weak signal portions of VHF/UHF), 28MHz is perfectly okay.
Personally, I like choices, so I've considered getting a 10MHz IF if I ever
got deep into transverters. This would in theory allow full use of both 2
meters and 70cm with the same radio, if not some higher bands. Of course, I
haven't looked into it too closely to see whether 10MHz is even workable
given that there's also a 10MHz clock input on the Q5 transverters, so any
thoughts on that would be good.

Thanks,

-Mooneer K6AQ

On Wed, Jun 2, 2021 at 6:34 AM W8JH <[hidden email]> wrote:

> I am looking to add the DEMI (Q5) transverter to my K3s and have no
> experience with transverters other than the internal one in my KX3. In the
> future, I may wish to progress to 2m EME as well.
>
> Here are some choices I need to make and I would appreciate any advice:
>
> Common IF vs Split IF. I'm thinking split IF with a K3s?
>
> Common RF or Split RF. Common RF for one antenna connection?
>
> IF drive level of -20 to 0dBm vs 0dBm to +20dBm. I think the K3s
> transverter output is 0dBm so I'm not sure what to think here.
>
> PTT polarity low instead of high I'm thinking.
>
> High stability Local Oscillator vs. standard.
>
> I could get a custom IF and I think there is some slight advantage to a
> 14mHz custom but I'm guessing the 28mHz standard IF is good enough?
>
> Thanks in advance for any advice or references.
>
>
>
>
>
> -----
> 73,
>
> Joe, W8JH
>
> K3s, KPA 500, KAT 500 and KX3 happy user.
> --
> Sent from: http://elecraft.365791.n2.nabble.com/
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]
>

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Dave Fugleberg

Re: K3s and DEMI transverter

In reply to this post by W8JH

I use three Elecraft and one DEMI transverters with my K3. All split IF at
28 MHz, single antenna path for each, PTT low.

I’d go with the high stability LO, especially at 432 or higher. The lower
level drive works fine with the K3 and I believe the K3S transverter
interface is identical in that regard. You can set it on a per transverter
basis to get the drive you need. If you intend to use the same transverter
on a different radio that does not provide a low level drive or a split IF,
your choices may be different.

One other thing to consider is how to select the active transverter if you
add more than one. The Elecraft transverters have that built in, as they
can read the Aux bus. For others you may need some external switching so
that you only key the transverter that is selected. I use a band decoder
from unified Microsystems for this. Of course if you connect only one
transverter to your K3S that’s not an issue.

On Wed, Jun 2, 2021 at 8:33 AM W8JH <[hidden email]> wrote:

Jim Brown-10

Re: K3s and DEMI transverter

In reply to this post by Mooneer Salem

On 6/2/2021 7:46 AM, Mooneer Salem wrote:
> From what I've been able to tell, for what most people use transverters for
> (SSB/CW on the weak signal portions of VHF/UHF)

Since the advent of WSJT-X, most weak signal work has been taken over by
these modes, and for some of them, frequency stability matters.

73, Jim K9YC
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Wes Stewart-2

Re: K3s and DEMI transverter

In reply to this post by W8JH

In all honesty I haven't been on 2-meter EME for 35 years. Gear was all
homebrew then. That said, I would stick with a 28 MHz i-f. You must consider
image response and where it lands with respect to other services. I once saw an
analysis that promoted a different i-f but I fail to remember what it was or
why. Definitely avoid anything lower.

I would split everything if you are ever to consider a separate HP amp and
mast-mounted preamp. If you are going to worry about frequency stability I
wouldn't bother with the high stability option. You can use an external source
that is much better. I wouldn't necessarily opt for a GPSDO without knowing its
phase noise performance, however. I put together a surplus (ebay) Morion OCXO
that I've had running for about six months and it has been within 3 milliHz of
10 MHz for several months.

I would suggest the low drive power input. You can always attenuate this. PTT
low to TX would be my choice.

Wes N7WS

On 6/2/2021 6:32 AM, W8JH wrote:

David Olean

Re: K3s and DEMI transverter

In reply to this post by W8JH

Comments below.....

On 6/2/2021 9:32 AM, W8JH wrote:
> I am looking to add the DEMI (Q5) transverter to my K3s and have no
> experience with transverters other than the internal one in my KX3. In the
> future, I may wish to progress to 2m EME as well.
>
> Here are some choices I need to make and I would appreciate any advice:
>
> Common IF vs Split IF. I'm thinking split IF with a K3s?
I would advise using split signal paths. All my transverters are rigged
up for a 0 dBm 28 MHz signal level on TX. I always plan a system that
has power levels such that if you leave the exciter rf drive level at
max by mistake, it still will not impact anything or blow anything out.
>
> Common RF or Split RF. Common RF for one antenna connection?
>
> IF drive level of -20 to 0dBm vs 0dBm to +20dBm. I think the K3s
> transverter output is 0dBm so I'm not sure what to think here.
>
> PTT polarity low instead of high I'm thinking.
PTT set for ground on transmit standard for all bands.
>
> High stability Local Oscillator vs. standard.

This is an individual choice as all crystals are not created equally. I
have a K3 with the garden variety ref oscillator. It is more than stable
enough for digital modes. The problem is typically the LO in the
transverter itself. Crystals drift as temperatures change. I have a 10
GHz transverter with a crystal oscillator and the drift from cold start
to warmup is about 2 kHz at 10 GHz. After it is warmed up, I see only a
few hundred cycles of ambiguity from day to day. It was stable enough
to make me not change over to a synthesized LO since sideband noise on
the synthesizers was not so hot. Others have had more trouble with
crystals drfiting all over the place. Not all crystals are created
equally. Cleaning the crystal blanks affects drift drastically.
Production methods vary.

Recently, I made some digital contacts on 222 MHz and found that my old
crystal oscillator in my DEMI transverter drifted a bit. I saw a 10-12
Hz drift after each JT65 transmit sequence. The problem is the power
amplifier inside the trnsverter that heats up the crystal over time. My
solution was to put a small 12 volt fan on the heatsink just above the
hybrid amplifier location. It cured the drift. After employing the fan,
people assumed that I was running a ref locked local oscillator.
Measurements indicate a drift of just a few Hz over time. At higher
frequencies, (over 432 MHz) some sort of reference oscillator
arrangement is needed for digital modes. Cheap 10 MHz sources are
available on EBay. Just make sure that whatever ref locked oscillator
you use, that it does not produce bad LO noise sidebands. I have a
proportional oven 10 MHz crystal oscillator made by Wenzel Associates.
It was cheap on EBay, and more than stable enough for any digital modes.
You do not need a rubidium standard at all.

>
> I could get a custom IF and I think there is some slight advantage to a
> 14mHz custom but I'm guessing the 28mHz standard IF is good enough?

I use 28 MHz on 50 thru 432. On 902 and above, I standardized on a 145
MHz IF for everything up to 10 GHz. 24 GHz has double conversion.

73

Dave K1WHS

>
> Thanks in advance for any advice or references.
>
>
>
>
>
> -----
> 73,
>
> Joe, W8JH
>
> K3s, KPA 500, KAT 500 and KX3 happy user.
> --
>

W8JH

Re: K3s and DEMI transverter

In reply to this post by W8JH

Many thanks for the replies. Here are my likely choices for the L144-28
transverter:

Split IF, seems the consensus.

Common RF, I don't think I want separate coax runs for TX and RX and will
only be using a single antenna.

-20dBm to 0dBm to lessen my chances of screw-ups which could fry something.

Low ground, 28 mHz IF and I will spend the $45 for the high stability
oscillator.

Now to find some quality RG58 BNC jumpers. I have tools for 0.4 inch coax
and don't want to invest in more tools for this stuff.

Thanks again to all.

-----
73,

Joe, W8JH

K3s, KPA 500, KAT 500 and KX3 happy user.
--
Sent from: http://elecraft.365791.n2.nabble.com/
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73,

Joe, W8JH

K3s, KPA 500, KAT 500 and KX3 happy user.

Stewart Bryant

Re: K3s and DEMI transverter

In reply to this post by Mooneer Salem

> On 2 Jun 2021, at 15:46, Mooneer Salem <[hidden email]> wrote:
>
> Personally, I like choices, so I've considered getting a 10MHz IF if I ever
> got deep into transverters.

I would be concerned that the 10MHz station reference would appear as an in band signal.

The other IF commonly used is 14MHz (by Kuhne for example), but we use 28MHz on all our VHF and up contest transverters. If you want to see how we do with this arrangement look up G5LK/P and G3M in the UK listing for the major portable contests.

Stewart/G3YSX

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Stewart Bryant

Re: K3s and DEMI transverter

> On 7 Jun 2021, at 15:31, Stewart Bryant <[hidden email]> wrote:
>
>
>
>> On 2 Jun 2021, at 15:46, Mooneer Salem <[hidden email] <mailto:[hidden email]>> wrote:
>>
>> Personally, I like choices, so I've considered getting a 10MHz IF if I ever
>> got deep into transverters.
>
> I would be concerned that the 10MHz station reference would appear as an in band signal.
>
> The other IF commonly used is 14MHz (by Kuhne for example), but we use 28MHz on all our VHF and up contest transverters. If you want to see how we do with this arrangement look up G5LK/P and G3M in the UK listing for the major portable contests.
>
> Stewart/G3YSX
>
>

I should add that we use Kuhne on 70cm and an HA1YA ME2T on 2m rather than the DEMI.

Stewart/G3YSX

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Edward R Cole

Re: K3s and DEMI transverter

In reply to this post by W8JH

Previous to 2010, I was using a FT-847 for 50,144,432 MHz and a DEMI on
1296 with 144 IF.

That was the year I bought my K3-10* (since updated with new synth). I
bought DEMI 144-28, 222-28, 432-28* and 1296-28 transverters as better
design filtered LO better making 28-MHz a good choice for use with my
K3. Note: * indicates use of PLL locked to 10-MHz reference resulting
in less than 2-Hz max drift on 28-MHz. Choice of LO frequency is
determined by ability to reject LO feed thru (primarily). Picking a too
low IF can lead to troubles.

I also have DEMI 3400-145* and 10,368-144* transverters. Use of 144 or
432 as IF at 1296 and above is common. They use the N5AC A32 PLL to
lock LO. The A32 is now NLA so look at DEMI digiLO as replacement.
Currently using an OCXO as 10-MHz ref but will switch to GPSDO this summer.

Eventually Elecraft will offer 144 and 432 transverter modules for the
K4. Will be curious what IF is chosen.

73, Ed - KL7UW

On 2 Jun 2021, at 15:46, Mooneer Salem<[hidden email]> wrote:

Personally, I like choices, so I've considered getting a 10MHz IF if I ever
got deep into transverters.

I would be concerned that the 10MHz station reference would appear as an in band signal.

The other IF commonly used is 14MHz (by Kuhne for example), but we use 28MHz on all our VHF and up contest transverters. If you want to see how we do with this arrangement look up G5LK/P and G3M in the UK listing for the major portable contests.

Stewart/G3YSX

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