- Registriert
- 23 Januar 2018
- Beiträge
- 154
- Punkte Reaktionen
- 11
- Punkte
- 18
- Alter
- 69
- Website
- www.vk2ji.com
- Verified User
- YES
- Rufzeichen/Call
- DD5LP
Hi Guys, here's something to look out for in case you make the same mistakes I did.
The main reason I bought the X108G was to use it for SOTA activations. Now that we're nearly at the bottom of the Solar Cycle, 20w rather than 5w of SSB can make a difference. I have been taking my FT-817 plus a drastically modified Ramsey QAMP linear amplifier to give me between 20 and 30 watts on 15m through 80m (switched LPFs etc.). That as well as adding weight to the pack also adds complications with additional cables battery etc. Hence the X108G in one unit makes a lot of sense to replace the 817 and the amplifier.
For the amplifier I bought a hard case 4S (4 cell) 5Ah LIPO battery. Yes I know LifePO4s are safer but they're still a lot more expensive than LIPOs. The other difference between 4S LIPO and LiFePO4 batteries is that the LifePO4 gives a nice 14v output whereas the 4S LIPO gives over 16v. For my amplifier this was fine as running the amp on 16v rather than 13.8v added about 5 watts to the output (the power transisters are actually meant to be run at 28v). However as I wanted to use this same battery now for the X108G, I needed to do something to reduce the, on full charge, 16.5v down to 13.8v otherwise this could damage the rig.
On eBay I came across a voltage reducing unit with a nice LCD display and it was programmable to give a set voltage and up to a current limit out for a range of voltages comining in (always reducing the voltage however - this is what some call a "buck converter"). Once it arrived I attached my needed connectors to it, programmed it to 13.8v output and 3.5 amps maximum current output.
Testing it, at first all seemed fine. It does not create RF hash as some of the voltrage-up converters do. When I took the power up on the X108G past about 13 watts output however I got a horrible noise seeping into the audio. 13 watts and below were fine but over that, the noise was there. I switched back from the battery and regulator to a shack PSU and there was no problem.
My thought was RF ingress into the processor in the regulator was occuring. So I added ferrites to all leads to and from the regulator - still the problem was there. Then I thought decoupling the supply with a couple of 0.01uFd capacitors might help - no the problem was still there. It looked like I would have to mount the regulator in a metal box to screen it from RF.
But then I did something that I should have done to start with. I watched the LCD display, and what happened when I turned the power up and transmitted? The voltage went down! KLING! How does the "buck" unit regulate an over current situation? It drops the voltage and it is known that the X108G does not like running at under voltage. I adjusted the "buck" unit to allow up to 5 amps current and no problems any more!
I'm happy it was simply a miscalcualtion on my part as to the cureent needed by the x108G when transmitting at 20watts output and nothing more serious - here's a picture of the hard case LIPO battery and the regulator:
73 Ed DD5LP.
The main reason I bought the X108G was to use it for SOTA activations. Now that we're nearly at the bottom of the Solar Cycle, 20w rather than 5w of SSB can make a difference. I have been taking my FT-817 plus a drastically modified Ramsey QAMP linear amplifier to give me between 20 and 30 watts on 15m through 80m (switched LPFs etc.). That as well as adding weight to the pack also adds complications with additional cables battery etc. Hence the X108G in one unit makes a lot of sense to replace the 817 and the amplifier.
For the amplifier I bought a hard case 4S (4 cell) 5Ah LIPO battery. Yes I know LifePO4s are safer but they're still a lot more expensive than LIPOs. The other difference between 4S LIPO and LiFePO4 batteries is that the LifePO4 gives a nice 14v output whereas the 4S LIPO gives over 16v. For my amplifier this was fine as running the amp on 16v rather than 13.8v added about 5 watts to the output (the power transisters are actually meant to be run at 28v). However as I wanted to use this same battery now for the X108G, I needed to do something to reduce the, on full charge, 16.5v down to 13.8v otherwise this could damage the rig.
On eBay I came across a voltage reducing unit with a nice LCD display and it was programmable to give a set voltage and up to a current limit out for a range of voltages comining in (always reducing the voltage however - this is what some call a "buck converter"). Once it arrived I attached my needed connectors to it, programmed it to 13.8v output and 3.5 amps maximum current output.
Testing it, at first all seemed fine. It does not create RF hash as some of the voltrage-up converters do. When I took the power up on the X108G past about 13 watts output however I got a horrible noise seeping into the audio. 13 watts and below were fine but over that, the noise was there. I switched back from the battery and regulator to a shack PSU and there was no problem.
My thought was RF ingress into the processor in the regulator was occuring. So I added ferrites to all leads to and from the regulator - still the problem was there. Then I thought decoupling the supply with a couple of 0.01uFd capacitors might help - no the problem was still there. It looked like I would have to mount the regulator in a metal box to screen it from RF.
But then I did something that I should have done to start with. I watched the LCD display, and what happened when I turned the power up and transmitted? The voltage went down! KLING! How does the "buck" unit regulate an over current situation? It drops the voltage and it is known that the X108G does not like running at under voltage. I adjusted the "buck" unit to allow up to 5 amps current and no problems any more!
I'm happy it was simply a miscalcualtion on my part as to the cureent needed by the x108G when transmitting at 20watts output and nothing more serious - here's a picture of the hard case LIPO battery and the regulator:
You must be registered for see images attach
73 Ed DD5LP.
