MRF1946 TEST CIRCUIT SCHEMATIC

zulu53 · Post by **zulu53** » Sat Oct 03, 2020 9:04 pm

BLW 60 amplifier presented by radium98 is a tuned one. Therefore, it does not correspond to what I am looking for. For a correct Google search he should have added the word "BROADBAND". That's how I could know that few years ago, some people have made a broadband FM amplifier, using BLW60 transistor.

zulu53 · Post by **zulu53** » Sat Oct 03, 2020 9:41 pm

Thank you Bton-FM for your suggestion on MRF101 Kit. It is really a very interesting and cost-effective device. However, RF hobby is more about building by yourself than simply buying. So, for the time being, I will still struggle with my old device. Maybe by mid-2021, I will try MRF101.

Albert H · Post by **Albert H** » Sun Oct 04, 2020 2:00 am

There is no broadband 4W in / 40W out BLW60 circuit. This device has difficulty in achieving 10dB gain in a critically tuned amplifier.

Stephen and I actually introduced an RF output "slope" to the Pro III exciter, as the gain of the BLW60 varied across the band. The Pro III delivers about 4 W at 87.5 MHz and nearly 5 W at 108 MHz! With this drive, the BLW60 amplifiers would deliver 40 Watts when tuned correctly.

Don't waste your time with broadband amplifiers with old transistors. There's no point. Also, don't try to copy that "Veronica" amplifier - the low pass filter won't work as the coils will just couple to each other, the driver stage is insufficient to push the 2N6084 to 40 Watts (it only has about 5.6dB of gain at Band II in a critically tuned circuit), and the cheap ceramic capacitors he's used will break down at the slightest hint of mismatch, and will fail anyway after time since they're not designed to be used in hot environments.....

How many PAs do you intend to build? Just buy some damn trimmers and build a simple PA with your '1946:

https://www.ebay.co.uk/itm/CERAMIC-TRIM ... SwGmtdmdKJ

radium98 · Post by **radium98** » Sun Oct 04, 2020 7:23 am

zulu53 wrote: ↑Sat Oct 03, 2020 9:04 pm BLW 60 amplifier presented by radium98 is a tuned one. Therefore, it does not correspond to what I am looking for. For a correct Google search he should have added the word "BROADBAND". That's how I could know that few years ago, some people have made a broadband FM amplifier, using BLW60 transistor.

Sorry i dont know just i have to put the word "BROADBAND" in front of my search,excuse me and my ignorance.
you see everyone is going to help you and this can not be done ,before i was searching for samething to eliminate the use of trimmer vishay that cannot be found theses days.i have few of them .
That's how I could know that few years ago, some people have made a broadband FM amplifier, using BLW60 transistor <<< you can ask them or post a picture to see how magic work of narrow band .
thanks.

zulu53 · Post by **zulu53** » Sun Oct 04, 2020 5:57 pm

I thank you very much for all your contributions. Now I'm quite clear about different possible options and about the way and steps forward.

I would like to thank Albert H for his deep input and also for sharing extensive information on RF components and devices.

I came to this topic because, after having read MRF1946 datasheet, some articles on italian electronics magazines and also some topics on the internet, I got excited about broadband FM amplifiers. However, I should have misinterpreted some data.

I was planning to build two 20-30W FM units and maybe a third one to be kept as a reference.

ln the event of getting one of the above suggested Mosfet amplifiers I believe a suitable driver will be needed. Maybe a 4W exciter. Therefore, I would appreciate if you could suggest a suitable modern circuit that could be used. Thank you

radium98 · Post by **radium98** » Sun Oct 04, 2020 7:13 pm

wideband

Albert H · Post by **Albert H** » Sun Oct 04, 2020 9:50 pm

The amplifier stages in the PLL Pro III are broadband - the 4427 driver is very under-run, and the 1947 has massive gain at Band II, so the two of them together take the ~50mW of the oscillator up to between 4 and 5 Watts (according to frequency) easily, in a no-tune configuration.

Hollings made is board "no tune" by over-driving two successive 4427s, guaranteeing lots of spurious crap. This is the approach that used to be used by some of the Italian rig manufacturers, and there were some (particularly the ones from Naples) that were really dirty!

The next job was to get rid of the VCO trimmer in the Pro III, so that the board could be tuned just by setting the switches. I have a couple of prototype boards here somewhere. We also planned to make the switches BCD-coded rotary types, so the user could just "dial up" the required frequency. I also did a nice ½" 7-segment frequency display board, which we were going to offer as an extra. There were plans for other "bolt-on" boards and hardware kits, but we never finished them, sadly.

At 1 Watt (1.25 W at the top of the band), we had just the right power level for some of the newer FETs around today. It's a pity that Stephen didn't live to see the MRF101!

zulu53 · Post by **zulu53** » Sun Oct 04, 2020 10:43 pm

Once again, I thank you for your detailed circuit description of PLL Pro III. I don't think I can make it, as it is. I don't have 50mW oscillator. However, I can build the amplifier stages with my 2N4427 and 2SC1947 transistors and use another oscillator.

radium98 · Post by **radium98** » Mon Oct 05, 2020 6:52 am

Here it is ,sadly without the output transistor ,becausei only find fake one .

radium98 · Post by **radium98** » Mon Oct 05, 2020 6:55 am

you can modify the vco by adding a few extra components like anothe varicap and few capacitor around ,then vco willbe voltage tuned .Similar to Bw 1w ,i could be wrong ,but i saw it in a smart kit modified transmitter.

zulu53 · Post by **zulu53** » Mon Oct 05, 2020 10:24 am

Thank you. I don't have 50mW used on PLL ProIII, but I have other options that I can use.

zulu53 · Post by **zulu53** » Mon Oct 05, 2020 11:07 am

Screenshot_20201005-113737.jpg

I would like to know what kind of shock can be used for RFC1 and FB3 / FB4. I only have VK200 and some 1uH, 5.6uH and 10uH molded coils. In addition, I have some flat 2X15mm ferrite rods.

zulu53 · Post by **zulu53** » Mon Oct 05, 2020 12:40 pm

* I mean, plain ferrite rods.

RF-Head · Post by **RF-Head** » Tue Oct 06, 2020 8:42 am

you can use VK200

zulu53 · Post by **zulu53** » Tue Oct 06, 2020 9:11 am

Thank you RF-head. Using VK200 for RFC1, that's what I was thinking about. What would you recommend for FRB3 and FRB4?

zulu53 · Post by **zulu53** » Tue Oct 06, 2020 9:37 am

I have also some 3X5mm ferrite beads with a small (0.7mm?) hole.

radium98 · Post by **radium98** » Tue Oct 06, 2020 1:12 pm

you can use them ,look at the bill material

zulu53 · Post by **zulu53** » Tue Oct 06, 2020 8:03 pm

Thank you radium98 for your suggestion.
Before posting my message, I have carefully read the "New Component List for 4 Watt PLL Pro 3XXX". It says:

FRB3, FRB4 - 5 turn ferrite bead. However, inductance values have not been displayed. My 3X5mm ferrite beads have a (0.7mm) hole. This is to small for 5 turn and for making those inductors.

RFC1 - RF CHOKE. Apparently, this is a resistor with 2 ferrite beads in each extremity with a enamel copper wire around it.

Unfortunately, is difficult to find out substitutes because the inductance values have not been displayed. That's the reason of my last post.

Albert H · Post by **Albert H** » Wed Oct 07, 2020 12:52 am

The values aren't critical. They just have to pass DC and block RF.

yellowbeard · Post by **yellowbeard** » Wed Oct 07, 2020 2:25 am

nrgkits.nz has the info on RFC1 - see here:
viewtopic.php?t=2255

MRF1946 TEST CIRCUIT SCHEMATIC

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