Up-conversion.

[Richard Kent]

Mike, I have been using a Kenwood MC-80 mic. I bought from a local ham.
While It is not a "hand mic", I use it where ever the radio goes. I don't
power it from the radio it has a battery case and I use that to power the
mic. Function keys, transmit lock, and a level that seems to match the
radio. Something to think about.

Richard Kent, WD8AJG

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[Bill Johnson-10]

I use a Heil mic which I ordered directly from Heil.  It is a great mic.  I
told them the rig I was using and they made sure I had the correct setup.

 
Bill
K9YEQ
 
K2-35 & 5279; KX1-35/3080
___________________________________
 
 
-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Richard Kent
Sent: Tuesday, August 15, 2006 7:53 AM
To: [hidden email]
Subject: RE: [Elecraft] Kenwood mic's



Mike, I have been using a Kenwood MC-80 mic. I bought from a local ham.
While It is not a "hand mic", I use it where ever the radio goes. I don't
power it from the radio it has a battery case and I use that to power the
mic. Function keys, transmit lock, and a level that seems to match the
radio. Something to think about.

Richard Kent, WD8AJG

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[pc5m, Carel]

Peter, Wayne

To add to the discussion of TX spurious signals:

I did perform extensive (spectrum) measurements on the TX spectrum at 28MHz
and found that (despite the class A / High IMD behavior of the TX buffer
Amp) some in band signals are generated in this amplifier.

Example:

TX = 29.0 MHz
Spurious found (only -40 to -50 dBc!): 28.51 MHz
Generated by: 2 * VCO - 4 * BFO = (2 * 24.085 - 4 *
4.915)

Spurious level is affected by the TX-ALC voltage and is worst at higher TX
power output. Also verified that this mixing takes place in the TX-buffer
and not in the (ne601) mixer itself and is due to the broadband design of
this TX-buffer (which is of course difficult to circumvent in this
architecture chosen). Placing an extra set of BPF's just after the TX-mixer
would solve the issue, but is not achievable in the present board layout. Of
course this would not improve the SSB/audio IMD as Wayne pointed out.

Because I use the K2 as driver of a 1KW+ VHF amplifier I have been very keen
in getting spurious signals as low as possible. Only way I could get the
spurious further down (60/70dBc) is to add an extra ERA9 amplifier (+10 dB
gain) just before the transverter IF output but within the TX-ALC loop. In
such a way making sure the signal level out of the TX-mixer and subsequent
TX-buffer amplifier are as low as possible.  
 

Cheers,

Carel,pc5m

> -----Original Message-----
> From: [hidden email] [mailto:elecraft-
> [hidden email]] On Behalf Of wayne burdick
> Sent: Monday, August 14, 2006 8:59 PM
> To: PE1E
> Cc: 'Elecraft Reflector'
> Subject: [Elecraft] Re: band-passfilter location in SSB transmit chain
>
> PE1E wrote:
>
> >
> > I was told that the absence of filtering between Tx  mixer and Tx
> > buffer
> > amp could cause annoying IM products.
> > ( The bandpass filters in the K2 are behind the Tx buffer amp., while
> > in at
> > least one of my other tranceivers in use here I see the bandpass filter
> > straight behind the Tx mixer without interfacing amp. ).
> >
> > Could this observation contribute adversely to the SSB Tx audio
> > quality (
> > in-band IM3) or do I see a ghost ?
>
> Peter,
>
> The TX buffer amp is operating class A, and any IMD it contributes will
> be completely negligible compared to the IMD contributed by the
> class-AB final amp. So, positioning the bandpass filters after the
> buffer should have no impact on observed IMD.
>
> If you see any more ghosts, let me know  :)
>
> 73,
> Wayne
> N6KR
>
>
> ---
>
> http://www.elecraft.com
>
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[wayne burdick]

pc5m, Carel wrote:

> I did perform extensive (spectrum) measurements on the TX spectrum at
> 28MHz...

> Example:
>
> TX = 29.0 MHz....

Hi Carel,

Thanks for the data.

While the K2 was never intended to cover the entire 10-meter band (we
spec'ed it in the manual at 28.8), it may be possible to attenuate the
indicated product at 28.51 with a modification to the buffer amp. Or,
it may be that the amp itself is not the cause, but is reflecting a
mismatch back to the TX mixer. A better match may be called for in this
case.

The way to check these possibilities is to temporarily terminate the
mixer and/or the buffer with a 51-ohm resistor, then check the spectrum
again. In either case, a 3 to 5 dB pad at the buffer's input or output
may substantially reduce undesired products. Of course the gain would
have to be made up after the pad (or after the band-pass filter).
Alternatively, you could replace the present buffer with a dual amp
(LT1253, I believe) and configure it for differential output drive
using a broadband transformer.

The K2 has been around for quite awhile, and it's nice to see operators
pushing the envelope with it  :)  Our policy has always been to keep
track of customer modifications (as well as our own) for possible
future inclusion in the kit. A recent example is the keying
modification, which resulted in the K2 having among the cleanest keying
envelopes of any commercial transceiver.

73,
Wayne
N6KR

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