Rohde & Schwarz

all-purpose SK1

for 1 kW shortwave operation
in any mode (1,5mc - 30mc)

formerly BOS tx at various locations

built in the early 1970s

 

 

 

 

 

 

 

 

Rohde & Schwarz

heavy duty shortwave class A
amplifier VK20 (1,5mc - 30mc)

formerly Bundeskriminalamt Wiesbaden

runs in combination with
the antenna matching device HS 9128

20 kW permanent output in any mode

power supply 3ph 400V approx. 60kVA

built in 1977

 

 

 

 

 

 

 

RF Power, AF Response & Intermodulation
Measurements for Transmitter 20 kW, type SK 20/3904

Operational Data

  Ua (kV) Iao (A) Ug2 (V) Ug1 (V)
SK1 3,0 0,35 460 -40
VK20 8,2 2,6 1200 -160

 

Vacuum-Tubes:


RS 1072 C   Ser# 3445 (SK1)
RS 1082 CL  Ser# 234 (VK20)


For all measurement procedures the transmitter is terminated by the dummy load RBN 60/60 .

 

RF Power Output operating in emission mode A1

Rated value: 20 kW

Measured @ power stage 'II' by vacuum-tube voltmeter URU with insertion head after automatic self-tuning:

 
f (mc) Pin (W) Uout (kV) Pout (kW) Ia (A)
1,5 220 1,11 20,5 5,2
2,1 240 1,09 20,0 5,2
3,5 215 1,12 21,0 5,2
5,4 240 1,07 19,0 5,2
8,3 205 1,09 20,0 5,4
10 250 1,08 19,5 5,3
13 280 1,09 20,0 5,3
16 390 1,11 20,5 5,4
20 350 1,08 19,5 5,2
24 280 1,09 20,0 5,2
30 180 1,07 19,0 5,1

 

Indicated Pmax with manual power setting @ decade exciter NO281 and adapting the anode overcurrent trip:

Pout = 30 kW @ 10mc for intermittent operation

 

 

Audio Frequency Response operating in emission
mode A3 with Pcarrier = 7,5 kW
f (kc) 0,1 0,5 1 2 4 6 8,4 16,8
Rated
value (dB)		 ≤ ±2,5 ≤ ±2 0 ≤ ±2 ≤ ±2 ≤ ±2,5 ≥ -20 ≥ -32
Measured
value (dB)		 -0,5 +1 0 +0,5 -1 -1 -60 > -70


Measured by RC Generator SRB & Millivoltmeter UVN

 

Spacing of intermodulation products 3rd & 5th order operating in emission mode A3J

Rated value: ≥ 41 dB vs. pep

Measurement procedure
The transmitter will be modulated by two audio signals with the same level which both @ a time drive the transmitter to 50% output.
After shifting down to the 10 kc stage the RF output signal will be recorded by the frequency spectrograph FNA.

 
f (mc) f1(kc) f2(kc) 2xf2-f1 2xf1-f2 3xf2-2xf1 3xf1-2xf2
      d3(dB) d3(dB) d5(dB) d5(dB)
5 1,21 3,6 45 46 67 69
20 1,21 3,6 42 41 57 60
30 1,21 3,6 42 41 58 60

 

detailed 3.6mc FNA spectrogram pdf (30 kB)

 

 

 

Siemens S97326

10 kW medium-wave
Broadcast Transmitter

formerly back-up tx NDR
Hanover

Pulse Duration Modulation

Final tube: 3CX10000
PDM tube: 4CX5000

compact dimensions

high efficiency

built in 1985

Edit:
transported to Ukraine and
set up in Odessa
see pic and clip,
transported on to Sitkunai/LTU
for 666 kc transmission

 


 

 

 

 


 

 

 

 

Telefunken TRAM 10

10 kW medium-wave
Broadcast Transmitter

formerly Antenne Saar 1179kc
Heusweiler

Pulse Duration Modulation

10 combined 1 kW amplifiers
with power MOSFETs

only one cabinet 200x60x100cm

very high efficiency (>80%)

built in 2005

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

R&S SK080 with classic anode/screen modulation, built in 1959
100% tube-based, 800 Watts RF, sucks 3.4 kVA (one phase!)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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