[AMRadio] AM transmitters for 15 meters that might be found in the UK?

[Larry Szendrei]

On 1/13/13 5:49 PM, Chris Wilson wrote:
>
>    13/01/2013 22:43
>
> This is my first post to this group, name is Chris and I am in England
> UK. I really like old gear and am converting a 2000D Henry RF
> generator on 27.1 MHz to a single band linear on 15 meters. Thinking
> ahead my next project would be to find and maybe fix up an AM
> transmitter and a "classic" AM receiver. What sort of gear could I
> look out for that will work at 15 meters and that is likely to be
> around here in the UK, as shipping vastly heavy gear across the
> Atlantic is not going to be very cheap or practical! Size and weight
> is not an issue if I can find it over here though. I am probably going
> to find more issues finding a Tx than an Rx. I don't want to spend a
> fortune, but do appreciate it may not come in "rice box" cheap,
> either. I have restored a Collins 30L-1 amp, and quite like Collins
> stuff, but remain very flexible.
Hi Chris,

Welcome to the group!

I'm pretty sure you'll get some responses to your query here, but not 
seeing any yet, I'll give you my 2 cents (or 2 pence) answer.

I'll assume you want to use the rig in conjuction with your linear 
amplifier project, and I'll also assume the linear will be running in 
grounded-grid configuration. If these are invalid please correct me. 
Although you didn't say so explicitly, I also assume you are interested 
in a "classic" (1950s - 1960s era) transmitter to pair up with the receiver.

My first choice of American gear would be a Johnson Viking Ranger I or 
II. Either will put out about 40W of carrier on 15M. The Ranger I covers 
the 27 MHz band, while this is replaced with 6M coverage on the Ranger 
II. This may or may not be too much to feed your amp, as the PEP output 
of the amplifier must be AT A BARE MINIMUM capable of 4X the unmodulated 
carrier output. Since this leaves no headroom for positive peaks 
exceeding 100%, I prefer to see a capability of at least 5X carrier 
output. Taking this into consideration you may have to run the Ranger at 
lower power, which is best accomplished by running the 6146 PA from the 
low B+ (HT). This can be accomplished by rewiring the accessory plug in 
the back of the radio without internal modification. Note you'll need 
some means of tuning up the linear at maximum output. Apologies if you 
already know this stuff. While the Rangers aren't light, they don't 
weigh as much as most of the amateur plate-modulated  transmitters of 
the era.

Another possibility is plate-modulated transmitters in the 100W class, 
of which there are many examples: Johnson Viking I or II (separate VFO 
is required unless you are planning on using XTAL control), Heathkit 
DX-100, Collins 32V series (I am not as familiar with these and don't 
know that they all cover 15M), Barker and Williamson 5100 come to mind. 
These are all much heavier transmitters (expensive to ship) and will 
provide too much signal to your amplifier without some modification.

A third option is screen-modulated transmitters such as the Heathkit 
DX-35, DX-40, DX-60, Cheyenne (MT-1), Knight T-50. There are probably 
more examples; these are the ones that come to mind. The power 
transformers can be prone to failure in the DX-35 and DX-40. Many (all?) 
of these transmitters employ controlled-carrier; if you don't like that 
they can be modified. These are smaller/lighter than the plate-modulated 
transmitters and typically put out about 15W of carrier (similar to a 
Ranger running off the low B+ supply as discussed above).

Geloso may have made some transmitters similar to the American units 
listed above, but I am not very familiar with their products. I only 
mention it because they may be easier to find in your part of the world.

I hope this is somewhat helpful.

73,
-Larry/NE1S