[amsat-bb] Leo Bodnar ICOM IC-9700 Reference Injection Board

[Mark Jessop]

In short, yes.

I have performed phase noise measurements on my IC-9700, with and without
injection locking. I am currently using a Leo Bodnar Mini GPSDO as the
reference, though using a MiniKits injection board (Leo wasn't selling his
at the time). I had to do this kind of locking as there was noticeable
drift when attempting 70cm EME contacts with the IC-9700 unlocked, which
was causing degradation in decode performance. With the radio locked there
are no issues.

The test equipment was a Symmetricom 5125A Phase Noise Test Set, and I was
using a 160 MHz Wenzel as a reference. The 5125A only works on input
signals up to 400 MHz, so for 70cm and 23cm I mixed the signal down to ~30
MHz using a Minicircuits LAVI-2VH, with the LO generated by a R&S SMA100B.
The rig was powered from 2x 100Ah batteries, and the GPSDOs were powered
from a 5V linear bench supply.

I tested:
- (2m/70cm/23cm) Unlocked IC-9700, transmitting for ~5 minutes to let the
drift settle as best as it can.
- (2m/70cm) IC-9700 + MiniKits Coupler board, driven with the MiniKits
GPS-9700 (+10 dBm)
- (2m/70cm/23cm) IC-9700 + MiniKits Coupler board, driven with a Leo Bodnar
Mini GPSDO (maximum drive, which is ~+10 dBm I believe)
- (2m only) IC-9700 + MiniKits Coupler board, driven with the R&S SMA100B
(+10 dBm)

Plots of the results are here: https://imgur.com/a/iFi527l

I guess the key point is that there is no degradation of transmit phase
noise observed when using any of the injection locking solutions. While I
did previously see some wide-band phase noise differences between the
MiniKits and Leo Bodnar LO's (as measured at 49.152 MHz), this doesn't
translate to a degradation at the output of the transmitter. I'm not seeing
the wide-band noise improvements when injection locked that others have
seen.

There appears to be a slight improvement in close-in phase noise when
injection locked with the GPS-9700 and Mini-GPSDO (and a big improvement
when using the SMA100B, but that sig-gen costs 20x more than the rig does),
but I wouldn't read too much into the close-in results as I only had time
to run each measurement for ~5 minutes or so. However, note that the
test-set noise floor (shaded area) is *well* below the measured results.

73
Mark VK5QI

On Sun, Feb 16, 2020 at 9:28 AM Kevin via AMSAT-BB <amsat-bb at amsat.org>
wrote:

> I wonder if anyone who has all the needed equipment to test has verified
> that the output of the 9700 is still clean after this mod?
>
>     In the past ext reflock boards compared the radios osc to a gps
> locked 10mhz signal and adjusted the trim voltage going to the vctcxo so
> levels were not touched, the radio was as clean or dirty as it was when
> it left the factory.
>    Now with this mod (if I understand it correctly) the main osc is
> still running and they are just pumping a much stronger signal into the
> master osc area until it drowns out the original osc and the radio locks
> to it.  So the question comes up are they then overdriving the osc chain
> downline and distorting? and is the original osc signal still there in
> the background now as noise?
>
> Might be a interesting project to find out.
>
> 73 Kevin wa7fwf
>
>
>
> On 2/15/2020 14:08, Bob Hammond via AMSAT-BB wrote:
> > This is a good explanation:
> >
> > "With the current firmware, users have observed frequency drift when
> using
> > narrow bandwidth modes. Using an external 10 MHz and the firmware reduces
> > the size of the frequency drifts by updating the corrections to the
> master
> > oscillator more frequently. The drift is still there,,,,, With the 49.152
> > MHz injector board and a good external 49.152 MHz GPS-locked oscillator,
> > the external oscillator locks the internal oscillator and the drift issue
> > is eliminated. The drift is probably not important on FM and most may not
> > notice the issue on SSB. But it is important to eliminate the drift if
> you
> > are using JT65 and similar narrow bandwidth modes."
> >
> > Copied from the Facebook ic-9700 group and a post by Peter Freeman in
> reply
> > to Tim Goodrich's question:
> > https://www.facebook.com/groups/163460540873662/
> >
> > Bob W7OTJ
> >
> > On Sat, Feb 15, 2020 at 1:53 PM Bob Hammond <propgrinder at gmail.com>
> wrote:
> >
> >> Eric,
> >>
> >> I found much information on the design and benefits of a GPSDO and
> >> reference board for the IC-9700 here:
> >>
> >> https://www.minikits.com.au/gps9700#wspr
> >>
> >> The Mini-Kits version is only slightly different than the Leo Bodnar
> >> version however the designs are virtually identical.
> >>
> >>
> >>
> http://www.leobodnar.com/shop/index.php?main_page=product_info&products_id=301
> >>
> >>
> http://www.leobodnar.com/shop/index.php?main_page=product_info&products_id=352
> >>
> >> Bob W7OTJ
> >>
> >> On Sat, Feb 15, 2020 at 8:16 AM kd8drg.admin--- via AMSAT-BB <
> >> amsat-bb at amsat.org> wrote:
> >>
> >>> I was wondering what the advantage is for using this board vs the
> >>> standard 10Mhz external reference on the 9700?
> >>>
> >>> 73
> >>> Eric
> >>> WD8KNL
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> _______________________________________________
> Sent via AMSAT-BB at amsat.org. AMSAT-NA makes this open forum available
> to all interested persons worldwide without requiring membership. Opinions
> expressed
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