Garey Barrell <[EMAIL PROTECTED]> made an utterance to the drakelist gang
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Maurizio -
Drakelist seems slower than usual today.
As Uli mentions below, the TR-4C has 8 pole filters and is as good as
the "late" TR-4s. The "early" TR-4s had the "soupcan" filter (two
discrete filters in one can, same as used in the TR-3) and suffers the
same level of unwanted sideband products as the TR-3 and the T-4X. You
can look inside the top of a TR-4(any) and under the LOAD shaft, you
will see two crystal filters side-by-side, either silver in color or
bright blue, mounted to a vertical bracket.
The unwanted sideband information, the "dirty" stuff, is the result of
wider filter skirts. The 4 pole or "soupcan" filter transmitters were
only spec'd for unwanted sideband suppression as "40 dB above 750 Hz"
and carrier suppression as 60 dB. The TR-3/"early" 4 was the same, and
only 50 dB for carrier suppression. By comparison, the T-4XB and 8
pole TR-4 were spec'd at "60 dB" for unwanted sideband and "60 dB" for
carrier, more in line with current standards.
The Icom 7800 says ">63 dB carrier suppression" and ">80 dB unwanted
sideband suppression". (And only $15k!!)
The IC-746PRO says ">40 dB carrier" and ">55 dB sideband".
The biggest problem with the T-4X is the low frequency "monkey chatter"
from the poorly suppressed unwanted sideband, mainly below 750 Hz.
Drake also issued "revised tuning instructions" in the 80's for all
their transmitters to recommend a maximum loaded plate current of 350 mA
for the TR-(any) and 340 mA for the T-4X(any) on the 160 - 15M bands to
comply with spurious emissions requirements of FCC Part 97.73, (now
97.307) which were "tightened" to ">40 dB suppression for ALL spurious
emissions". These have been further tightened in the last couple of
years to >43 dB. Fortunately transmitters built before 1978 are
exempted from these regulations!
By the way, NONE of these specifications affect CW operation with the
T-4X(any) or TR-(any).
73, Garey - K4OAH
Atlanta
Drake C-Line Service Manual
<http://hr99.home.mindspring.com/R-4C_Servicez/>
Graf Ulrich Com MD PD ST 2 ULM 1 wrote:
Graf Ulrich Com MD PD ST 2 ULM 1 <[EMAIL PROTECTED]> made an utterance to the
drakelist gang
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Hello Maurizio,
I once owned a TR-4C and operated it for many years. With an appropriate
microphone and careful level adjustment I never got any critical audio reports.
So the signal must have been rather clean.
73 Uli, DK4SX
-----Ursprüngliche Nachricht-----
Von: Bollini, Maurizio [mailto:[EMAIL PROTECTED]
Gesendet: Mittwoch, 8. Juni 2005 13:15
An: Graf Ulrich Com MD PD ST 2 ULM 1
Betreff: RE: [drakelist] Drake Differences
Thanks Uli for your answer.
I guess that in TR-any it could be due to the balanced modulator, at first.
I'm still interested to know if TR-any performs similar to T4X in term of
"dirtyness" of the transmitted signal.
73 Maurizio, IZ2CED
-----Original Message-----
From: Graf Ulrich Com MD PD ST 2 ULM 1 [mailto:[EMAIL PROTECTED]
Sent: mercoledě 8 giugno 2005 12.05
To: Bollini, Maurizio; Drakelist Mail (drakelist@www.zerobeat.net)
Subject: AW: [drakelist] Drake Differences
"Dirty" ssb signals have nothing to do with rf harmonics. They are caused by
audio harmonics and inband intermodulation in af and rf stages. Both are created by
overload of mic amp, balanced modulator and rf amplifiers.
73 Uli, DK4SX
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