Low drive control to modern amps

Steve G1XOW

HI, I'm just about to purchase an SPE expert 1.3K solid state amp. These thing have very very high gain (20-24dB) and are designed to be driven around 5-10w input max. Accidental drive of 100W will almost certainly **** the amp in seconds.

I'd assumed that SmartSDR would have the sensible facility to set a permanent TX power out limit / override, e.g a control in initial radio settings that would limit TX power to say max of 10w under any circumstances regardless of power-out slider.

I can't find such a limiter so what now?  I would have thought this would be a base-line feature given digital trends and solid state amps?

73 de Steve G1XOW

KY6LA_Howard

First. Driving a SPE 1.3K with 100W will NOT **** the Amp. SPE Amps are famous for their design to prevent such events. At worst all it will do when overdriven is automatically reduce power output to mid or lower ranges. second, SPE offers a FCC version of the 1.3K with only 15 dB Gain for the USA market where we still have to deal with anachronistic anti-CB rules. I am sure you could pick up an FCC version Third, DDUTIL already offers exactly such a power limiter feature called Autodrive... I have been using it for years to limit my 2K-FA to legal Limit 1,500W.

DV

I have the the Flex 6700 and the SPE 1K FA amp and in the Flex setup mode it has a little known throttle control which can be used to limit the output power of the amp.  It does this through the CAT connection to your computer/radio. To set up the 1K FA, you must be in the Flex mode, then you must have the amp in the "Operate mode", then you can adjust the percent power you want to feed to the amp using the up and down arrows.  When you do this a little pop-up comes up on the amp LED that gives you what percentage you are using. (Not sure how percentage tracks with actual power from the radio in watts from the radio, but its pretty close.)  Once entered on each band the 1K FA will remember the setting for each band as long as you have CAT working. You can even adjust the power input to the amp in this manner while transmitting, if it needs adjusting. 

I don't know whether the SPE 1.3 FA has the same feature, but it's worth a try.  I showed this feature to the SPE sales guys at Orlando Ham fest and they had no idea the amp would do this. I have DDUTIL and find it very helpful, but I do not use it to adjust input powers.

KY6LA_Howard

as far as I know a Neither the 1.3K or 2K have any sort of sophisticated API implemented as is found on the 1K Rather SPE provides a totally inadequate software package that emulates it's front panel controls rather than giving you full API access to the Amp like the 1K. The will respond to band data over CAT but. Little else That said, DDUTIL Autodrive does the Job extremely well for me

Jon_KF2E

I noticed in the brochure for the SPE 1.3 FA that it says over 30000 lines of software to make it the smartest amp out there. If they have a totally indaquate software what are they doing with all that code? Calculating π to the last significant digit?

Jon...kf2e

Steve N4LQ

Doug: Where is this throttle control? Can't find.

KY6LA_Howard

The code is used for protection and tuning control of the amps The software on both the 2K and the 1.3 do not provide for an API like they had with the 1K Hence it is difficult to remote those amps as you do not have direct control through an API. What you get is a Front Panel Emulaor which is a piece of software that mimics your Front Panel on you Local Computer ONLY. I have o use Paralles Access to control my Amp is there is no native way I can turn it on or off thru an API. Bottom Line: totally Inadequate.

DV

Steve, as posted by Howard, apparently only the 1K FA will do this.  If you have the 1K FA amp, here's the pertinent information from my post yesterday with some clarification...

To set up the 1K FA, under the CAT "Setup Options",  you must be in the Flex-Radio CAT mode.  Use the "Set" button to open up the 'Setup Options' screen, then select "CAT", then select 'Flex-Radio' on the 'Set CAT' window, then select the 'Baud rate' for CAT (I use 9600 Baud).  Then, you must have the amp in the "Operate" mode (push the 'Operate' button) and you must be transmitting, you can then adjust the percent power you want to feed to the amp using the up and down arrow buttons just to the left of the "Set" button.  When you do this, a little pop-up comes up on the amp LED (just above the 'Band" readout that gives you what percentage power you are using. Once the power is adjusted for each band, the 1K FA will remember the setting for each band as long as you have CAT working. You can even adjust the power input to the amp in this manner while transmitting, if it needs adjusting. 

KY6LA_Howard

@Steve Thank you Steve for posting this issue You motivated me to do something about it. I went onto the SPE relecrtor this morning to ask Gianfranco YET AGAIN when they were finally going to fix the lack of API for both the 1.3K and 2K The Good News is that SPE promised TODAY that they will be shortly releasing an API for both the 1.3K and 2K so you may likely be able to control the 1.3K and 2K via DDUTIL if you really need to. Do things like use your computer adjust your power gain.

Steve G1XOW

Howard,

Thanks for the reply, and I look forward to getting the 1.3k with the newer smart firmware. However, my point was that it would be so easy to limit the drive of the Flex, and has other benefits too.

In the old-school (knobs and dial) days, all I would have to do is to pop the lid off and adjust a potentiometer to limit output, but now with SDR all those "engineering" settings are denied from us.

Ironically, the output on the Flex 6k is already being limited, as the final PA is capable of much more than 100W out.

So the code to limit and re-scale TX output against the power output slider is already there and working. The only bit missing is the user access to this control. I would guess no more than about 10-20 lines of code in the radio set-up screen would do it.

I don't need DDutil for anything else, and think it's really unnecessary for such a simple ask. Surely Flex are not expecting us all to become API/3rd party programmers to fix such simple user access/control issues?

73 de Steve G1XOW

KY6LA_Howard

Steve In my long experience the apparently simple things always turn out to be the most complex. I believe there already is a set power level in the API which is how DDUTIL sets its auto drive levels. Anyways you will end up needing DDUTIL to control the new API for your 1.3K as SPE is only providing the API notControl programs

Peter K1PGV

 I would guess no more than about 10-20 lines of code in the radio set-up screen would do it.

Less.  But the radio firmware would have to have a corresponding API implemented, and the new setting would have to be stored on shutdown and restored on startup.  And then you'd need a way to clear it, preferably without having to invoke SSDR.

Steve N4LQ

How about making a resistive T-Pad to absorb the extra power and just run the Flex wide open? You would be running the transmitter within it's design range. No more concern about accidents, software glitches or spikes. 

Bill W2PKY

Problem with pads, the received signal is reduced unless an additional T/R switch is provided. 

Steve G1XOW

The API is already there and being used by DDUTIL. Surely the whole point of SDR is that  these features are quick and easy to implement without having to resort to external hash-ups and bodges like T-pad and relays etc.

I've been a computer engineer for over 30 years, and a Microsoft Certified System Engineer since Server 2000, so to me this feels like childs play for the SmartSDR team compared with some of the heavy stuff they deal with.

KY6LA_Howard

The API is available. You can always write a special case power 1.3K settings yourself. Or just use DDUTIL Frankly I do not understanding what your problem is with using DDUTIL which already does EXACTLY WHAT YOU WANT.

Larry _ NY8T

DDUTIL gets the Job done!