Juma PA1000

[VK3FFB]

Hi

I am a new owner of a PA1000 HF linear amplifier. I did not see a dedicated PA1000 topic here, so I created this one.

I am quite happy with the PA1000. So far I used it on 20m and 40m in SSB and CW. I find it easy to use and it performs very well. My rig is an ICOM 756 Pro III. Given that the PA1000 must not be over-driven, I put a caution label at the RF power control of my transceiver. For proper drive level, I needed to set the RF power control to about 9 o'clock. I find the adjustment of PA output power level a bit problematic, so I am considering using an external power attenuator. Perhaps 3dB attenuation will increase the PA output power adjustment comfort. It would of course be better, if the transceiver had an extra output at drive level of 5 to 10 Watts. I wonder whether there are any other known solutions for this problem.

tnx & 73

Dee, VK3FFB

[W1CQ]

Hi Dee,

Seems you are looking for finer control of output for lower power settings since the transceiver level may not give such control in that range. (I'm driving the PA1000 with just 5-10W using a KX3 so there is more adjustable range).

You likely know alot on RF power overshoot with certain transceiver models, so the conservative approach seems to be to keep the MAX EXCITER PWR setting at 100W until you are certain about transceiver characteristics, using a peak reading wattmeter.

You can see the PA1000 User Manual (Block Diagram) shows built-in attenuation of 3 dB fixed plus 0 to 7 dB adjustable.
AD5X describes this In-Line Attenuator http://www.ad5x.com/images/Articles/HiPwrPad.pdf
If you do add external attenuation be sure it is robust and that it cannot be accidentally switched out - to avoid risk of overdrive.

Anyway just wanted to say hi to another PA1000 user,

73 de W1CQ RYAN

[VK3FFB]

Hello Ryan
apparently, I did not get an e-mail when you replied to my post. Thanks for your response & the link.

Meanwhile, I got used to the 9 o'clock position of my RF output power control knob. I only touch it when I switch between SSB and CW because on CW I usually stick to 200W.

It's a different ham life with the PA1000. Getting good reports and faster response when calling CQ. Glad I chose the PA1000 over other options I was considering. On CW I can happily run full power (200W) at SWR = 2.0 without power reduction by SWR detector circuit. I don't use any tuner.

73
Dee, VK3FFB

[sm0jzt]

Hi there
I finally could connect up my PA1000 (to a Expert Electronics SunSDR2 Pro).
The band change and PTT stuff works as a charm and the PA is putting out a healthy 1kW with a 15W drive.

Anyway, I find it a bit odd that the PA gous out of "operation" status after a band change. one needs to enable the operation every time.

The only resolution to this is to enable "operation" as default (after unit power up).

Isnt there a better way ?

B.r / Tilman D. Thulesius SM0JZT

[OH7SV]

Hello Tilman,

The switching to STBY state when changing a band is a default safety feature. That can be modified in the Service Pages so that PA1000 will stay in OPER state when changing a band and also when powering up. See more in the user manual found here www.jumaradio.com/juma-pa1000

73 Matti OH7SV