Clicking when using main VFO knob 6400M

Erik Carling EI4KF

I have had my 6400M for one week, mostly used on static frequencies for FT8. Today, when I was tuning through a band, I noticed that the main VFO knob has a click as it is turned. With 10Hz steps there are 3 or 4 clicks per 1khz and each alternate click is louder. The actual tuning function is ok but the clicking is annoying. The 2nd VFO knob is totally silent in operation. Is there anything I can do about it?

Erik Carling EI4KF

The radio is being returned to the dealer, apparently it has a mechanical failure. 🤔

Mike-VA3MW

Erik

Glad they are taking care of it for you. If it hasn't left yet, you may be able to look under the VFO knob by pulling off the rubber cover from the knob and then using a Key (I can't remember if it is Torx or Allen) to pull the knob off if that is something you are comfortable doing.

Part II is that if it is in the actual encoder then that is a bit. more complicated.

Just a thought, Mike

Erik Carling EI4KF

Hello Mike,

It goes tomorrow. I have tried to the remove rubber cover but I just cannot get it to slide forward. I am afraid of stretching it or pulling on the shaft too much. So I will have to leave it to the dealer who is in the UK whilst I am in Ireland so it is a pain but one of those things. It is probably best that someone qualified looks at it. I suspect it will actually need internal inspection as the 'clicking' is from the inside. Anyway, thank you for taking an interest.

73 de Erik.

Erik Carling EI4KF

The radio arrived at the dealer yesterday and they found a securing nut was loose on the main VFO, presumably due to vibration during the transporting from USA to me via the dealer.

I also reported a sudden reboot issue which occurs only on 20mtrs with 40 watts of transmit power. All other bands are perfect up to my licence limit of 1500 watts. So it is very strange that it is so susceptible on 20mtrs. I had traced it to the ethernet cable which, since the radio has been away, I have replaced with a screened cable. I have therefore yet to see if this makes a difference. The dealer have emailed Flex about this issue and will wait for a reply before sending the radio back to me.

If anyone has any experience of RF issues affecting a Flex radio (6400M in my case), I'd be grateful to learn of them together with solutions. As I said, I have replaced the ethernet cable which was definitely the culprit and I have acquired a stack of clip-on ferrite cores to add to that cable if needed.

VE7ATJ_Don

Hi Erik... while I don't have any personal experience with a 'reboot' issue, the fact that it only occurs on 20m seems to point to your conclusion that it is RF getting back to the wrong places in the radio (hence your replacement of the ethernet cable). Also maybe take a look at the antenna and its SWR on 20. I have already read/heard of problems like reboots/drops in power when the radio encounters particularly high SWR. You don't mention if your radio has an ATU, but while the Flex ones are pretty good, they're only rated to handle up to a SWR of about 2.5 or 3 to 1.

Also, think about ferrite cores on the power supply cables and your connection from the power supply to the wall.

Erik Carling EI4KF

Hi Don. The antenna is an Ultrabeam dynamic so it has low SWR across it bands 20m-6m. It is 40 feet AGL but the mast is only 70 feet from the radio room so I daresay that doesn't help. Though 40 watts just on 20m is strange. But I like your suggestions for the power supply - good advice, thank you - I will do it.