Radio Air C.I.T. ERB 281

PA2JF
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Radio Air C.I.T. ERB 281

Messaggio: #31978 PA2JF
09/11/2018, 21:01

Hallo,

Two weeks ago i bought a Radio air C.I.T. ERB 281 from a friend of my. He bought the transceiver to restore it but found the radio to heavy(140 Kg) The ERB 281 is a great radio for everyone how loves fine mechanics, as i do very much.

The first time i switched on the transceiver i did not get it to work at all. After some Googling the only serious peace of information i found here made by IK5NXD and I5HGM. Thay did a great job decoding the transceiver and thay had a lot of documentation about the radio; great. Its quite funny that the schematics thay had are from a better quality than the ones i got from a friend of the German army.

On my Facebook-group i started to collect all information about the tranceiver i got a big collection of photo's i took wile dismantling the transceiver to clean everything there was to clean. I opened every part te clean an make photo's. You can find the photo's i took here: https://www.facebook.com/groups/247151519285948/

Now everything is cleaned and put back together there is starting to be some life in the radio. After some mails to and from IK5NXD made me clear there are some logic steps to help to understand how far the transceiver is working.
- First i had to start-up the transceiver in 'duplex receiving' mode to see if the synthesizer is working properly. That is working fine for now, I translated a peace of the german manual that described how to align and test the receiver but it works, it tunes and i got ether noise and some voices form time to time.
- Next was going into Simplex Send & Receive. Now the fun part starts in thought but was happy too fast...... Here the problem begins;
When starting up the transceiver the synthesizer wil tune to chosen frequency from a gear network that works as a sort of preset. If al the mechanisms work like planed it will tune to the right frequency. Im receiving the same on the transceiver as on my SDR-stick so im sure i can say that that peace works. After the tuningsproces in the receiver part the tuning begins in the linear amplifier and antenna tuner. Here is my problem; sometimes this will work more times it wont. When it works i get a green ready ligt within a minute or so. If not the amplifier is going to send a quite strong (full antenna current meter) carrier signal to find its alignment. After a few second this is a bit less and after about a minute the linear amplifier wit shut-down. After restart usualy the same again. When leave the set for a longer time it will tune usualy quite good.

The question now is, wat is the purpose of transmitting the strong signal and why does the amplifier shut down.
The next time i startup the set i will start-up my spectrum analyzer to see whats happening.

Please feel free to think with me and please ask if you want more info.

73, Joeri, PA2JF

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IK0MOZ
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Re: Radio Air C.I.T. ERB 281

Messaggio: #31979 IK0MOZ
10/11/2018, 9:24

For general info, referring the ERB 281 set, in the BLOG area there is the following file :
ERB-281_001_REV-001_27_06_2014.pdf
ImmagineImmagine # ARO 301/0Immagine WS 19 Group # 15 Mario IK0MOZ

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Re: Radio Air C.I.T. ERB 281

Messaggio: #31982 PA2JF
10/11/2018, 15:43

Thank you IK0MOZ, i got the file emailed from IK5NXD.

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Re: Radio Air C.I.T. ERB 281

Messaggio: #31984 ik5nxd
10/11/2018, 21:29

Hi Joeri
it is normal that when the transmitter or the antenna coupler don't reach the correct tune the rig shuts down, it is a protection to avoid damage to the components.
The set shuts down also if there is a SWR between the tx and the antenna coupler in eccess of 1.3, if I remember well.

the set does the followings steps to tune the transmitter:

1) the tuning cycle of the tx is started with the homing both the tx and the antenna coupler.
2) then the driver is tuned,
3) the power amplifier is tuned, the set switch the antenna output on the dummy load inside the antenna-coupler, you can see this in the ANTENNENSTROM
the needle go slowly at about the midrange of the scale.
4) after few seconds you can hear a click, the antenna relay switches from the dummy load to the coupler circuits, and the coupler beging to tune the antenna.
you can see the ANTENNENSTROM swing fron right to left until the tune is correct, at about midrange of the scale.
5) after the tune is reached the set stay for few second in this state and then the control pass to the operator, and the green light is on.

if until step 4 everything is ok, and if you are using the antenna, may be a mismatch in the antenna that the coupler can't compensate.
you may try changing the jumpers at the transmitter, they are used to insert series capacitors at the antenna.
They are behind the front cover, and there are two jumpers for each band to insert capacitor C31306 and/or C31307 and/or C31308
If you are using a dummy load instead of the antenna then the thing are more complex.

if the problem at step 3 , then may be a problem of autooscillation or a problem with the ALC.

Let me know
73
Andrea IK5NXD
ImmagineImmagineARO # 310/5 Andrea IK5NXDImmagineImmagine

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Re: Radio Air C.I.T. ERB 281

Messaggio: #32016 PA2JF
12/11/2018, 17:35

Hay Andrea,

I tested yesterday and with the information you supplyed i think that the radio is working ok, at the end of the mounth i will buy a new depole for 80 to 10 meter and will test again. My antenna now is not the greatest(grc-9 antenna). If the SWR has to come witin 1.3 after tuning, i need a better antenna.
I will post the results at the end of the mounth.

73,

Joeri PA2JF

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Re: Radio Air C.I.T. ERB 281

Messaggio: #32018 IK0MOZ
12/11/2018, 17:45

Hi Joeri, let us have some photos of your "Monster". Few people knows the ERB281. Mario/IK0MOZ
ImmagineImmagine # ARO 301/0Immagine WS 19 Group # 15 Mario IK0MOZ


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