On 31 Jan 2002, at 22:56, Steve Ellington wrote:
> good enough for a code reference but not so for keying. As for the
> Pegasus...I was refering to the transmitted signal, not the received.
OK, we have established that the Pegasus [and Jupiter] sound pretty
good on receive when a decent sound system is used so I decided to
take a close look or, listen as the case may be, to the transmit signal.
My first test involved running my Peg into a dummy load at 10 watts
and sending a LONG file via CW. I then went into the workshop
"shack" at the other end of the house and listened to the signal on
the following receivers......Collins 75S3, hallicrafters SR-400A
Cyclone, Drake TR-4, Ten Tec CorsairII and finally Ten Tec
Paragon. On each receiver, the signal was mid scale on the S meter
so I was receiving a realistic level. Each receiver was attached to a
short antenna which prevented any "outside" QRM. In other words,
I was able to concentrate on my transmitted signal without
The signal sounded pretty good, in fact, I thought it sounded very
good. Yes, some slight phase noise [I think] around the edges as I
tuned through the signal, but a very nice signal. One I would be [in
fact I am] proud to put on the air.
OK, that test finished I came into the lab at work and rigged another
test just to see if my ears were very far off base, and to obtain some
data as everything up to this point has been pretty subjective.
The test setup consisted of a Jupiter transmitting 10 watts into a
dummy load with a -20db isolated coupler into a fixed 15db
attenuator and a step attenuator set at about 66db. The isolated rf
signal was then fed to a battery powered CRYSTAL controlled
receiver with no agc and with with very low noise and distortion. I
don't know the exact bandwidth of the crystal controlled receiver
but it is somewhere around 2Khz. Output from the crystal controlled
RX was then transformer isolated and fed to a harmonic distortion
analyzer. In normal operation, the distortion analyzer is adjusted to
completely remove the fundamental frequency from the equipment
under test and anything left is considered harmonic distortion. In
this case, the crystal controlled receiver distortion products are so
low as to be insignificant, so anything left after nulling the
fundamental signal from the receiver is transmitted noise, phase or
In the following tests, the signal source was set to provide the same
output from the crystal controlled receiver in each case. I did run
the power up to full power momentarily to see if it made any
difference in the transmitted noise. It did not.
Here are the results as indicated on the distortion analyzer:
Jupiter - 1.1%
Logimetrics analog signal generator - 0.6%
Ten Tec Paragon - 0.5%
Omni D C series - 0.4%
Crystal reference oscillator - 0.09% [This is reaching the limits of
my measuring ability]
Tapping the Jupiter case caused the distortion measurement to jump
to a little over 2%. Tapping on the desk where the rig was sitting
caused little or no change. The signal generator was very bad in this
respect and the Omni D was very good.
It is clear that the Jupiter [and Pegasus] transmit some phase or
other kind of noise. It is also clear that the amount of noise they
transmit is of no consequence in all but the most exacting of
applications, whatever that means. :-)
It is also understandable that the Jupiter is worse than the Paragon
because the Jupiter has two VCo's to cover 30 Mhz whereas the
Paragon has four to cover the same range. So the Jupiter VCO tuning
sensitivity is twice that of the Paragon. I don't know if there is any
connection, but with twice as many VCO's the Paragon has
approximately half the transmitted noise.
But even at 1.1% transmitted noise, the Jupiter is pretty nice. Let's
see..........that's 0.011 to 1 or about -40db close in........very close in.
In the "old days" 30db quieting on an FM receiver was considered
full quieting. Or put another way, one has to look for the noise
before it is noticible. In fact that seems to be the case. This does
not seem to be an issue until someone starts talking about it which
draws attention to it and then it is an issue. Kind of like a fly speck
on the ceiling, not noticible until someone points it out. :-)
In closing, I can only say that every day I use either my Pegasus or
Jupiter, I enjoy them more and I give Ten Tec a great big thank you
for producing such fine gear at such affordible prices. And to think
that the best is yet to come!!!!!