I don't know how much you care about the external MPX, but I have a small transmitter board that makes about 10mW and uses the QN8007. It sounds fantastic to me with the integrated stereo (better than any of the BH chips). It has an SMA connector just like the one you have, so it shouldn't be hard to connect. There is no way to use MPX because everything is integrated in the chip, but it is a very high quality chip. It sounds as good as a professional to me. The only small problem is it will occasionally click with really high frequency audio, but if your 15 khz filter is working, it should be fine. I'd still use stereotool just with the MPX turned off.
I designed the board a few years ago and I was going to make an amp to go with it (similar to the thing you have), but I didn't have the time. Let me know if you're interested in one and I will build the PCB for you. It may take a week or two.
How much would you charge for that? I'm quite interested. Sure, I'd love to have MPX, but if it's the difference between being off the air or being on at full power, I'll obviously take the latter.
Thank you, by the way. You've been a wealth of good info
How much would you charge for that? I'm quite interested. Sure, I'd love to have MPX, but if it's the difference between being off the air or being on at full power, I'll obviously take the latter.
Thank you, by the way. You've been a wealth of good info
I'll charge you $50 with free shipping. It will take 2 weeks. I haven't built one in three years, so I got to locate the materials and firmware.
If you decide to go with it, you might want to check out ebay for some small SMA attenuators. Unless you have a way to measure milliwatts from that current board you have. I suspect it to be on the order of 10mw or less considering it seems to use an RD01MUS1 for the preamp. 10mW shouldn't hurt it, but you might find that the adjustable power on my driver does little or nothing because it's over driving. Maybe buy a -6db, -10db and -20db attenuator to try. But don't worry about that now.
It runs on 12V connected to one of the two headers you see in the corner. The other header is for powering the LCD board you see below. Then you just connect the green and yellow wires labeled SDA and SCL. Wrap these wires on a ferrite bead. I will include a bead for you. Make sure they are well wrapped and that the antenna is as far as possible from the board. If you do not, you will notice the screen becomes unresponsive and requires off and on to work again. This is from too much EMF, so either move antenna or put it in a metal box.
Let me know. . .
(right click and view image, it doesn't show the whole thing)
I forgot something important. It is very possible that the current board uses the driver for SWR protection. It is possible that it turns off the amp, but I think it may send the signal for the driver to turn itself off. If this is true, then SWR protection will no longer work if you install my board.
I forgot something important. It is very possible that the current board uses the driver for SWR protection. It is possible that it turns off the amp, but I think it may send the signal for the driver to turn itself off. If this is true, then SWR protection will no longer work if you install my board.
Okay, I apologize for the delay in response.. Had some significant personal issues and didn't do much with radio during that, but I'm getting back on track.
I finally got back out there and tested some stuff out. The good news is SWR and watt output still displays with the T251 as it's source. Amplifier didn't kick on until I was pushing about .5w.
The bad news is I already fried the amplifier. Was running a low pass between the transmitter and the amplifier, since it maxes out at 125w. I've been having an issue where the filter shorts out if its in certain positions (it's a sealed cylinder, but the case is rusting and getting flimsy, so not much I can do to fix it). Which is another reason I didn't want to run it on the output, thought it'd be safer on the input.
Well, it shorted. The amplifier didn't appreciate it, even on input, and refuses to amplify anything now.
It's possible something else went wrong, that's my best guess though... But I ordered a replacement SD2931, hoping that fixes it. Probably in over my head yet again, but that's how I roll
In the meantime, a question on your board... How is it with spurs and spectral purity? The t251 into the 160w was absolutely demolishing and trashing the band, and obviously that's not desirable. I turned it on to test a few things, but clearly not going to run it like that consistently. The BH1414K was much cleaner than the BH1415F in the t251, and if this is comparible or better, then yep, 100% on board with that.
Edit: based on what I'm seeing, it's likely the RD01MUS1 may have been damaged... I can probably jump over it and just run the exciter at 1.5w instead, at least according to the spec sheet for the next amplifier in the line, the RD15HVF1. Nice quick patch in the meantime, but certainly I'll want to replace the RD01MUS1... If that's what it is, the picture isn't clear and it's no longer light enough out to trek out there to get a better picture of the board with a better camera.. but I'll mess with it a bit tomorrow.
Okay, jumping the RD01MUS1 worked. Had another really dumb oops moment, forgot to turn down the t251 and caused some smoke and glowing to appear on the amplifier board, but shockingly, putting it back at the right level and she's able to push 200w just fine.
A few notes: the t251 is putting out absolutely horrible awful spurs all over. No shocker there. Saw some all the way up to 140mhz even with the LNA off on my RTLSDR, This is with a low pass filter... It's just so bad.
Good news is I was able to get a replacement RD01MUS1 for $2, though it'll take a month or two to arrive.
This is all a learning process, and I'm certainly learning.
I mean, honestly I'd love to figure out why the frontend on the HLLY itself sounds so awful, but SMD soldering is still something I have a very losing ratio with, so I'll decline for now.
Okay, jumping the RD01MUS1 worked. Had another really dumb oops moment, forgot to turn down the t251 and caused some smoke and glowing to appear on the amplifier board, but shockingly, putting it back at the right level and she's able to push 200w just fine.
A few notes: the t251 is putting out absolutely horrible awful spurs all over. No shocker there. Saw some all the way up to 140mhz even with the LNA off on my RTLSDR, This is with a low pass filter... It's just so bad.
Good news is I was able to get a replacement RD01MUS1 for $2, though it'll take a month or two to arrive.
This is all a learning process, and I'm certainly learning.
I mean, honestly I'd love to figure out why the frontend on the HLLY itself sounds so awful, but SMD soldering is still something I have a very losing ratio with, so I'll decline for now.
Interesting story!
I dare say the rig is leaking badly but at that wattage and I guess proximity(?) the sdr is creating its own spurs.
Have you tried tuning in a receiver some distance away and listening across the dial? Or better still take the sdr out in the car and test across the fm dial plus 2nd and 3rd harmonic freqs when you're a mile or so away. See if that makes a difference.
Imo, you're asking for trouble but I may be wrong and in so many ways I'd be happy to be proven wrong ;-)
I dare say the rig is leaking badly but at that wattage and I guess proximity(?) the sdr is creating its own spurs.
Have you tried tuning in a receiver some distance away and listening across the dial? Or better still take the sdr out in the car and test across the fm dial plus 2nd and 3rd harmonic freqs when you're a mile or so away. See if that makes a difference.
Imo, you're asking for trouble but I may be wrong and in so many ways I'd be happy to be proven wrong ;-)
So on the "try a mile away" aspect, with only 25w from the t251 itself and listening on a car radio, I was seeing interference on a station almost a mhz away for about a mile and a half. On the plus side, it's a very rural area so that isn't a huge issue.
I did not have an SDR at the time, or a laptop capable of running one, when I tested.. I do now.. My whole setup is remote controllable from my phone now, so I can drive out a few miles, turn it on, and pull out the laptop/SDR and truly test it out. I will likely do this tomorrow, weather dependent.
I will note, 30w with the tx-30s (bh1414k) caused much less frontend overload and interference on my radios in-home than the t251 (bh1415f) does at 25w. I could still pull in a station 400khz away that was about 80km away, now I can barely pick up a 50kw station 2mhz away that's only about 13km away. And that was when the transmit antenna was sharing the roof... So the difference between the bh1415f and the bh1414k truly is notable. I saw one of Ogre's posts elsewhere saying the QN8007 is even better, so certainly there is room for improvement
I wish they'd stop using the bh1415f, the bh1414k isn't that much more expensive
I dare say the rig is leaking badly but at that wattage and I guess proximity(?) the sdr is creating its own spurs.
Have you tried tuning in a receiver some distance away and listening across the dial? Or better still take the sdr out in the car and test across the fm dial plus 2nd and 3rd harmonic freqs when you're a mile or so away. See if that makes a difference.
Imo, you're asking for trouble but I may be wrong and in so many ways I'd be happy to be proven wrong ;-)
So on the "try a mile away" aspect, with only 25w from the t251 itself and listening on a car radio, I was seeing interference on a station almost a mhz away for about a mile and a half. On the plus side, it's a very rural area so that isn't a huge issue.
I did not have an SDR at the time, or a laptop capable of running one, when I tested.. I do now.. My whole setup is remote controllable from my phone now, so I can drive out a few miles, turn it on, and pull out the laptop/SDR and truly test it out. I will likely do this tomorrow, weather dependent.
I will note, 30w with the tx-30s (bh1414k) caused much less frontend overload and interference on my radios in-home than the t251 (bh1415f) does at 25w. I could still pull in a station 400khz away that was about 80km away, now I can barely pick up a 50kw station 2mhz away that's only about 13km away. And that was when the transmit antenna was sharing the roof... So the difference between the bh1415f and the bh1414k truly is notable. I saw one of Ogre's posts elsewhere saying the QN8007 is even better, so certainly there is room for improvement
I wish they'd stop using the bh1415f, the bh1414k isn't that much more expensive