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Kirk_t
New member
Username: Kirk_t
Post Number: 1
Registered: 6-2012
| | Posted on Saturday, June 16, 2012 - 2:17 pm: | 
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I have a LDO 100 watt Bilinear Amplifier. (Long Distance Operator made in Council Bluffs Iowa) It was made in the 70’s or 80’s I have it installed but would like some instructions on operation. I am hoping someone can help me.
It has four switches Linear on/off, Pre Amp on/off, Mode AM-FM/CW-SSB and Modulation PEP/RMS. I understand what position the Mode AM-FM/CW-SSB switch needs to be in but I am not sure about the others. Should the Linear on/off and Pre Amp on/off be turned on and off with each other and used simultaneously or does one provide a function without the other? I also don’t know what position the Modulation PEP/RMS switch should be set in or what that function does, can someone help me with these questions. Thanks Kirk |
Philuk
Junior Member
Username: Philuk
Post Number: 33
Registered: 4-2009
| | Posted on Wednesday, July 11, 2012 - 12:40 pm: |
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Hi Kirk, I am no expert by any means but the pre amp would normaly only be used when opperating in SSB mode as it will only make the background noise louder on AM/FM (although on VHF which is less noisy I do sometimes use a preamp on FM to pull up weak signals)
The modulation switch sounds to me to be some sort of bias for the linear keying, PEP for AM SSB where it peaks and falls and RMS for FM and possibly PSK where there is a constant duty cycle and no fluctuation, I may be wrong but thats how it seems to me after recently building an RF sencing automatic linear keying board where a tantalum bead capacitor is switched in and out for either SSB or FM (no AM used here)
Give it a try on a low power feed and if it chatters when in SSB mode try the mod switch in the other possition as that is what the switch does on my board.
regrds
Phil
26WF183
M6MRP
M6MRP Yaesu FT817nd, FT840 FT51R.
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Philuk
Junior Member
Username: Philuk
Post Number: 34
Registered: 4-2009
| | Posted on Wednesday, July 11, 2012 - 1:29 pm: |
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Hi again Kirt forgot to answer another of your questions, the linear side of the amp is for transmit only and the pre amp side is for receive only, so as you transmit a relay switch inside will bypass the pre amp circuit and route your signal through the amplifier TX transistors or tubes, you can infact use the pre amp alone to boost your received signals by whatever the rating of the pre-amp is 15db 25db? without the linear amp side being switched on or vice versa use the linear amplifier to boost your transmited signal varible up to its max output (dont expect the full 100W) depending on your input feed (check how much input feed it is rated to take some are very low power input even as low as 3w)
The chatter I mentioned will be the relay switch switching between receive and transmit if there is not enough RF power to hold the relay open on TX that is why the modulation switch is fitted as on AM/ssb the dead carier without modulation could be lower than required RF power to open the RX/TX relay, Start low and work your way up watching the output of the linear on a wattmeter after the liner and when you reach about 80w with modulation you are getting close to the correct RF input, also make sure your swr is low as a high swr will fry the linear, another thing quite a lot of these 100w quoted linears only quote the SSB peak output so FM would usualy be only half of that, expect 30w to 45w on FM unless its a real good one then you may get near 100w on FM and more on SSB, good luck and hope that helps.
Phil
M6MRP Yaesu FT817nd, FT840 FT51R.
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Sitm
Intermediate Member
Username: Sitm
Post Number: 471
Registered: 1-2004
| | Posted on Monday, July 16, 2012 - 3:59 pm: |
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I have one of this units and they operate very nicely, you should be very pleased. They work great as a driver in pep mode. |
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