AM17/AM18 LINEAR AMPS

[VK4FLR]

Hi ,
Does anyone out there have any conversion details/or experience with the Ex DCA/Airservices Australia series of Linear AM Amplifiers, - I am mainly interested in the AM18 which is a solid state version of the popular AM17.

These AM18's have been withdrawn for service around Australia.

The Aviation Ident is Y5/2966 & was made by Collins Radio Co Melbourne Aust for Airservices (DCA) & is Branded "VHF-50 Linear Powere Amplifer " . Has its own exciter , which has frequency setting DIP switches allowing operation 118 -135mhz .

The Amp is 19 inch rack size with a built in rugged 24v power supply . I have the Handbook & circuits for the unit , but having some problems working out how to modify it for amateur 2m ssb service , I am sure the amp would be capable of at least 200w pep as each PA transister (2N6369) are rated at 80w max & there are 2 aircooled PA modules each with two transisters & 2 x output combiners (Anaren IJ 0280-3 - 100/160mhz )from each PA module ..

Grateful for any info or assistance

Thanks & regards Frank VK4FLR .....contact me at email froden@westnet.com.au

[vk1da]

The website http://vhfdx.radiocorner.net/ has some articles of interest to VHF operators including an article about the AM17 at http://vhfdx.radiocorner.net/docs/AM-17.pdf, written by Ian Cowan VK1BG.

I have not seen anything about the AM18.

[VK4FLR]

Hi Folks ,
just an update to my original post in Nov 2009, Information has come to hand from a VK3 who also has obtained a supply of the obsolete AM18's & kindly contacted me a few months ago with some very useful & helpful information regarding mods for 2m ssb operation. Thanks Wayne !

To cut a long story short , there is a Collins factory module jumper card available that plugs in to replace the Air-band 2w exciter module & allows RF drive from a rear-mounted N connector which then feeds into the Driver & PA modules (2 x 2N6369 in each PA module ) . I simply fed 2w from an old FT290r on 144.1mhz into the rear connector & with minor adjustments to the driver attenuator & high power alarm setting -easily obtained 50w rms into a dummy load . Bandwidth doesn't seem to be an issue & no adjustments have yet been done to the pA cards ?

After fitting a coax relay harness & sequencer , I expect to obtain at least 200w pep output. Some further testing is required to ensure min loss from the LPF 2nd & 3rd harmonic filter as the 3db ref point is supposedly 150Mhz . The Anaren combiners for the drive & output PA's are rated for 100-160mhz .

I also plan in the future to drop in a 200w LDMOS pallet to replace existing PA modules in a spare 2nd AM18 for 70cm , the 24v DC supply is capable of approx 26amps I believe .

I have pics & circuits of the Collins jumper card & of the AM18's if anyone is interested ?
Regards
Frank VK4FLR

[ADMIN]

I have pics & circuits of the Collins jumper card & of the AM18's if anyone is interested ?

Frank, you can easily post them in this topic, as attachments.
Topics posted here rank quite well with Google Search, so the information can be shared well beyond emailing back to just a few.

Post once - read many.

[VK5GF]

G'day All,

I have an AM17 transmitter for sale, in working order, fitted with antenna relays, 3W in for 300W+ out 144Mhz.

Complete with original service manual, offers please, this unit is in a rack and is heavy, location Encounter Bay SA 5211

Cheers,

Jeff VK5GF/8GF

[VK4FLR]

Hi Adam , yeah thanks was a bit reluctant to have a crack with the pixs so I didn't stuff up which I have a habit of doing as an old timer & these infernal confusers ??- so will have a crack- fingers crossed ?/
Frank

[VK4FLR]

Hi in addition here is the Internal layout of the AM18
as per previous post ?
73's Frank

[VK3IH]

[quote="VK1DA"]The website http://vhfdx.radiocorner.net/ has some articles of interest to VHF operators including an article about the AM17 at http://vhfdx.radiocorner.net/docs/AM-17.pdf, written by Ian Cowan VK1BG. quote]

Link no longer works does anyone have Ian's email or a copy of the above notes?

Paul

[VK3BJM]

Link no longer works does anyone have Ian's email or a copy of the above notes?

Ian's email is shown on his Op Info in the VK Logger (and it's correct).

Some time back ago I scanned my copy of the AM17 handbook into a PDF. I can either put it up here for download, or send it direct, if it would be helpful.

I also have copies of the notes Ian made (somewhere) and also some extras that Chas VK3PY noted from his experiences with tweaking the beasts. They might take a bit more searching for, to find the soft copies...

73,
Barry
VK3BJM

[VK4FLR]

Paul -I have a copy of Ians article re the AM17 in PDF format not sure how to attach it here - will send it to your email address
73
Frank VK4FLR

[VK3XL]

Frank can you send me a copy as well to
vk3xl at yahoo dot com dot au

[VK3XL]

Dont worry Frank, I have got it via the way back machine.
for anyone else interested here is a link

http://web.archive.org/web/201505130417 ... orner.net/

main site

http://web.archive.org/web/201505130417 ... orner.net/

[ADMIN]

... not sure how to attach it here - will send it to your email address

Attaching a file to a post takes less than 10 seconds and a few mouse clicks.
This procedure makes it look harder than what it really is: http://www.vklogger.com/forum/viewtopic ... 63&t=10023

[VK3IH]

And here is the PDF for posterity......


Paul VK3IH

[VK4FLR]

Thanks Guys - sorry Adam - I knew there was a way ! but a bit slack here because of my old age -& lack of knowledge of confusers ?? will follow that procedure next time !!
73
Frank
VK4FLR

[VK2JDS]

Does anyone have any info on the Collins VHF50 linear power amplifier? circuit, mods. power output etc
this one is solid state, but looks like the AM17 rack unit
I would be greatly appreciative of any help on this
73 Dave vk2jds

[VK4FLR]

Hi Dave
Please scroll up this thread & read my initial posts & mods info etc -the VH50 linear amp is known as a AM18 amp (solid state sister to the AM17) -I have a copies of the manual & schematics , but too many to copy -currently running one on 2m ssb with about about 300w pep. In the process of mods for a 300-400w drop in modified PA module for 70cm with an additional AM18 . They are well built & require minimal mods for conversion to 2m!
73
Frank
VK4FLR

[VK2JDS]

Thanks Frank, i didnt realise the vhf50 was in fact the AM18.
Your ealier posts should get me started on it once i get the bypass circuit in place. It all apears unmodified so hopefully it will work.
If i get stuck i will send an email etc, just watching the snow falling here...... a good day to do inside work.
Thanks and 73, Dave

[VK3IH]

Now have my AM17 up and running all jerry rigged but putting out 300W+ PEP.

Happy man, I am using FT817 to drive it (had to use a relay before sequencer).

Paul

[VK2PIR]

Hi everyone,

I just inherited one of these beasts and I was wondering if Barry VK3BJM or anyone else may be able to send me a copy of the handbook for the AM17 amplifier.
Thanks in advance.

73s

Alex
VK2PIR