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PostPosted: Mon Aug 31, 2015 6:01 pm 
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Joined: Fri Aug 21, 2015 4:14 pm
Posts: 28
Hi Jim,
Got my board today. Looks great.
I will be uploading firmware soon, any idea when Ver 1.4 will be out?
Any updates or details on the PA? You have me drooling
I have a real UV3 that is in the hospital now so I am having slum with my TM742. ;-)
This is a great concept and trying to decide how I am going to do a Standalone UI for it. There are so many options. I could use the STM32-SDR http://www.stm32-sdr.com board with a code rewrite. Use the new STM32F7 discovery board. Or the http://imall.itead.cc/nextion-nx2432t043.html.

It should be easy either way its only software ;)

Keep plugging away on the Amp.

Thanks
Dave
VE7HR / VE7PKE


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PostPosted: Tue Sep 01, 2015 5:51 am 
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Joined: Mon Jul 23, 2012 6:25 am
Posts: 1143
FB Dave,

I can remember looking at the Drake UV3 when it came out and wishing that I could afford one!

I have finished the layout of the amp and I have the prototype PCB in hand. I just started building up the various pieces for testing.

As for specs, the amp will use the Freescale MW7IC008NT the info is here:

http://www.freescale.com/products/rf/rf ... :MW7IC008N

The data sheet says 11W @ 100 MHz and 9W at 400 MHz

Since the device uses 28V there will be an on-board DC-DC converter that only runs during TX and accepts 9-16V input. I've designed the output filters using Coilcraft 7 element filters optimized for low-loss but the filter switching uses Skyworks PIN diodes so there could be as mich as 1 dB loss between the output of the amp and the antenna jack.

The good news is that the MW7IC008NT is spec'd as a linear part is with FM we can drive it into compression (as long as the harmonics don't get out of hand) and if you look at figure 6 on page 6 of the datasheet, it looks like both the 100 and 400 MHz curves saturate maybe a dB above 10W.

We'll see how good a job I do and how close to this I can get. The data sheet guys tend to write specs based on measuring at the output pin of the chip, I have to get through biasing, filtering, switching, a power detector and the output jack before I can write my spec and I have to deal with component tolerance.

73,
Jim WA2EUJ


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PostPosted: Tue Sep 01, 2015 11:31 am 
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Joined: Fri Aug 21, 2015 4:14 pm
Posts: 28
Hi Jim,
That is a cool part. I am now even more excited. That has application many other places as well like on a UHFSDR ;-) I love 220MHz sideband.
Funny things about the Drake UV3's the prices are crazy on eBay.
Mine has a checkered past. It was given to me 25 years ago as a slightly damaged unit. ;-) It was hit by lightning. Had to change every piece of silicon. every diode, every bipolar and most of the IC's. 2 of the three PA's. Quite a chore. But worth it in the end. It is needing a recap job as the tantalums are getting fragile. It had character.

I shall wait for an update.
Thanks for doing this great project.
Dave
VE7HR / VE7PKE


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PostPosted: Fri Sep 04, 2015 7:49 am 
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Joined: Fri Sep 04, 2015 7:31 am
Posts: 17
Ha !!!!

Another UHFSDR user looking for AMPS ....

I'm building stand alone amps for each band .. but would rather have something that covers all 3 bands in a single amp .... or more, i see that its rated to 900Mhz too ... wonder if it can do 1.2Ghs. Though its looking for 100mW of drive and my UHFSDR only delivers 25mW right now ....

Maybe use the same relays used for in the HFSDR for the input ....

and take the hit on price with relays for RF output .... (i would not like to see the loss of pin diodes)

i don't know how much omron gsy-1 are but im running 40W on 2M through them.

Anyways .. looking forward to what you come up with ...


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PostPosted: Fri Sep 04, 2015 3:32 pm 
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Joined: Mon Jul 23, 2012 6:25 am
Posts: 1143
The prototype board is here and I've started working on the various sections:

3.3v Regulator - check
Glue logic control signals - check

Directional coupler - a bit of innovation here I call it a lumped element equalized, multi octave, microstrip directional coupler or LEEMMDC. It provides -45 dB coupling with 20-25 dB directivity from 120 to 470 MHz it's 0.6" long and costs <$1 on the board. Works just like the model predicts, the loss is a dB or so more at 450MHz so I may fine tune before the final design but in any case the radio will be able to measure it's output power and SWR

RX path - from the antenna connector, through the DIRCO, PIN diode T/R switch, Skyworks AS-179 input switch and back out a short piece of coax:
RX ON TX ISOLATION
146 0.9dB -53dB
222 1.2dB -48dB
445 1.4dB -45dB

No bad, I'll be less when I pull out the test points.

9-16V to 24V DC-DC converter - it works, still load testing to see what it'l do under load. Interesting that the shutdown pin turns off the converter but the output goes to the input voltage not 0V. It's OK because I'll bias the LDMOSFET off and the only real reason to turn it off is to prevent switching noise.

I've got the parts mounted for the amp but haven't tried it out yet. Maybe later this weekend.

The Coilcraft samples shipped today, they are a pain to deal with but the make the best coils.

I'll post updates as I get them.

73,
Jim WA2EUJ


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PostPosted: Fri Sep 04, 2015 4:18 pm 
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Joined: Fri Sep 04, 2015 7:31 am
Posts: 17
Which bias T did you go with ?

the conical one or the one advertised for a bias T ? (im going to try a bcr221 with a hmc482 --uhfsdr output)

Oh .. never mind .. i see that FreeScale didn't use coilcraft on the output bias T .. but Toko ....


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PostPosted: Sat Sep 05, 2015 7:16 pm 
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Joined: Mon Jul 23, 2012 6:25 am
Posts: 1143
This part is unlike anything I've ever used before. The data sheet doesn't even give the schematic for the eval circuit. I had to figure it out from the parts placement. For now I copied it exactly and I'll tweak from there.

Jim


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PostPosted: Sun Sep 06, 2015 6:21 pm 
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Joined: Fri Sep 04, 2015 7:31 am
Posts: 17
I hate to admit it ... this might not be so good for UHFSDR users ....

The uhfsdr should only put out 22dbm ... and i think that's a tottal sum of power .. i could be wrong ....

The UHFSDR has a fair amount of power on its 3rd and 5th harmonic .....

The last time i had my UHFSDR measured on a HP spectrum analyser it was only putting out 19dbm on 2M ....

PDF lists 100Mhz input for 11W out @ 27dbm ....that's 8db more than the UHFSDR(mine) can deliver .. with no losses on the input that puts the output at aprox 2W... and gets worse as you go up in freq .....

I like the idea of this part... just wish it had just a bit more gain ... ie a lower drive level ....

In a couple weeks ill test my UHFSDR with the for mentioned wide band Bias T sold by CoilCraft and see if the power increases .... but i have the feeling it will not, but will flatten out my power out across the lower or lost bands with the hodgepodge setup im using now ....

Guess this post really dosn't belong here ... but if the tri-band amp turns out the have rated performance ... then UHFSDR useres might have a hard decision to make .... depending on cost i sapose ...


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PostPosted: Sun Sep 06, 2015 9:16 pm 
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Joined: Mon Jul 23, 2012 6:25 am
Posts: 1143
I sure hope that you are reading that wrong because the RS-UV3 only makes about 23 dBm. I think that 27dBm in the data sheet in in the 'Absolute Maximum Rating' area. In the typical performance area it lookk like the 100 MHz gain at 11W CW is 23.5 dB which means the drive is less than 20 dBm.

Also look at figure 6 on page 6, if the 100 MHz line is at 11W at 23.5 dB gain then if I compress it (I'm only concerned with FM for the RS-UV3) to where the gain drops to 20 dB, it look like it should make 12 or 13W. So after switching and filtering I'mm hoping 10W at the antenna jack. We'll see.

I applied bias and RF to the prototype last night and I was using a 3.3V logic signal which couldn't get to the proper IDQ but I ran it at 7mA for stage 1 and 7 ma for stage 2 and with 20 dBm from my siggen it made 38 dBm on 146 MHz, 35 dBm on 222 MHz and 31 dBm on 445 MHz.

That's pretty encouraging!

I'm setting up a 5.1V zener to try increasing the bias and I can press a RS-UV3 into signal generator service for 3 dB more drive.

As for discussing the UHFSDR, go right ahead. It's in everyone's interest to find more applications for our products!

73,
Jim WA2EUJ


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PostPosted: Sun Sep 06, 2015 10:17 pm 
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Joined: Fri Sep 04, 2015 7:31 am
Posts: 17
that's encouraging ...

Yea i did read the gain for 400mhz max ratings (pg2) the gain goes up, not down, then 900mhz looks like max 38dbm ..

So 6.3W for 20dbm input on 146Mhz ... is that with 24V or 36V VDs2 ?

For some reason i thought that 3.3V (highest VGs voltage i seen was 3.5V,pg3 stage 2 characteristics) was max for bother control pins ....

Perhaps with more drive the Iq1, Iq2 will approach what was listed .... but who cares really .. id assume as long as max is not passed .. all is good.


Do you have anything that outputs 900Mhz to see how this amp performs ?

(oh miss read.. changing the UV3.... the PDF is abit confusing to me)


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