Operating

Antenna Analyser MFJ-266B Question
Antenna Analyser MFJ-266B Question avatar

An antenna analyser question. I have a MFJ-266B, note the “B”, the later improved version, and have had it for checking HF antennas for about 10 years. It always gives the same SWR as a meter on HF, so I have never suspected it, or doubted it, until today.

Today, as it is my birthday, and I fancied spending it playing radio, I thought I would have a go at making a home made mobile 2/70 antenna on a quick release to go on my cars mag mount.

With all the components assembled, I am expecting a 1/4 wave to be between 19″ and 20″ to be resonant around 145 MHz and 435MHz ish.

The analyser shows the 19.4″ whip to be resonant at 113MHz, 130MHz, 446MHz, and 471MHz. No amount of adjusting the length of the whip causes the analyser to deviate from these resonant frequencies.

These numbers just don’t look correct. Surely, the UHF readings should be somewhere near a multiple of x3 of the VHF resonant frequency.

Putting my 10m antenna on the car, it shows a resonant frequency with the analyser of 28 MHz, which is expected, as I also use this antenna for UK FM CB as well as for 10m.

I have never used this analyser for VHF and UHF before, and I am suspecting it is not reading correctly above HF.

Has anyone used an MFJ-266B for VHF/UHF before? And, how accurate are they on these higher bands?  Thoughts everyone please…

 

Kindest 73’s,
Mark M0INI
mark@m0ini.radio

#AntennaAnalyser #MFJ266B #M0INI

Operating

Operating Mobile CB 22/09/2024
Operating Mobile CB 22/09/2024 avatar

On a Sunday, I take my son to his Taekwando lesson.  Parked up waiting for Samuel, so, mobile today doing some CB for a change, what with the storm and the strong Russian stations clearer than UK ones, it was very difficult when only running 4 watts. Unfortunately, I don’t speak Russian.

I can hear Rob 59ST02 in Greece clear as a bell on channel 40, from the island of Rhodes, but, other stations just stomp on my replies! So I never got an over with him.

With a Thunderpole whip on a mag mount, a slightly off SWR of 2:1, and all this heavy rain, I was really struggling.

For next time, I will see if I can get the SWR lower, I used to achieve an SWR of 1.2:1 when I used the same antenna on a roof rack mount.  Oddly, my SWR is higher with the mag mount.  I would have expected the other way around.

Until next time…

73 de Mark, 26TM998
“Spark Transmitter”

EDIT: The SWR is now down to 1.2:1.  It was found that there was some tarnish on the centre pin of the coax from the antenna.  Overhauling both ends brought the SWR down nicely.

Events, Stafford and District Amateur Radio Society

Scouts JOTA 2024
Scouts JOTA 2024 avatar

This year, I am helping at my son’s Scout group, the 1st Ashley Air Scouts along with the local amateur radio club from Stafford and District Amateur Radio Society who will be taking the lead and providing the radios.

The global 2024 JOTA, this year, is being held between Friday 18th and Sunday 20th October 2024.  However, the event I will be helping will be on the Saturday 19th October 2024 between 10:00 and 16:00.

I have spoken to Scouts in years gone by, usually when I have been mobile, however, this will be the first time I have actually helped at an organised JOTA event with a Scout group.  Needless to say, both myself and my son are looking forwards to it.

EDIT: I understand a special event callsign has been applied for and granted for this event.  The callsign will be GB1SDS.  Listen out on the HF bands for this callsign on Saturday 19th October.

Website

Website Tidy Up
Website Tidy Up avatar

I have finally found some time to add some green to my logo (for the website) as the normal M0INI part is black, but this wouldn’t show on a black background theme.

I have also found time to update the text on my website due to the UK amateur radio license changes, and the removal of the mention of my air band radio license now that I am no longer a helicopter pilot.

I must remember to keep my stations website more up to date..!

Radio Rallies, West Manchester Radio Club

Red Rose Summer Radio Rally 2024
Red Rose Summer Radio Rally 2024 avatar

Red Rose Summer Rally 2024
West Manchester Radio Clubs summer Red Rose Rally

Yesterday, as club secretary, I visited the summer Red Rose radio rally organised by my club, the West Manchester Radio Club.

The clubs usual hall was out of action, so we were asked to hold it in a much smaller room.  It was quite tight getting all the vendors into such a small space, however, it it was managed.  Our chair, Les, was busy with his own stand, so I was asked to thank everyone for coming and do the raffle draw with the RSGB.  Lamco and the RSGB were sponsors of the raffle,  and a small digital hand hand was raffled at the event.

All in all, a lovely little radio rally and I am proud to be the club secretary.

In order to visit the next rally, please see this link…  https://wmrc.co.uk/rally.htm

Radio Repairs

ICOM 725 HF Rig
ICOM 725 HF Rig avatar

Some advice please…

I have a mint ICOM 725 all mode HF rig with all the bells and whistles (well for a classic rig), and it has all the ICOM options you can add to them, but, it has started with a curious fault that has me puzzled.

All the back lights on the front panel are not working, but, 10 years ago, these were changed to 12v LEDs due to blown blubs at the same time the rig was opened up for 5MHz transmit.

The rig works fine, and has for the last 12 years of ownership, but, only recently with no LED back lights to the front panel.

Today, I took it apart, to trace the fault, and I appear to have a short circuit across the LEDs, no other work has been carried out on the rig for 10 years.

According to the service manual, I should see a voltage of 11.5v to the back lights that are regulated down from 13.1v with two transistors and voltage divider resistors, see the relevant section of the diagram.

I am seeing 0v on this line and there is a very light smell of plastic burning, but, I can’t tell from which component. This line is showing a short to chassis.

My question is, do (or can) transistors just burn out and go short circuit to ground, well all current flowing to ground? What is the best way to test these in circuit, or, do I need to de-solder?  I look forward to hearing from someone so that I can get this classic rig back on the air again. Being so lightweight, I love it for both shack and portable use and is my favourite old HF rig.

EDIT

The plastic burning smell is from the square chip immediately behind the frequency display, and it appears to be an ICOM only part.  Searching the Interwebs, this appears not to be available.  Perhaps I could search for another “parts donor” ICOM 725.

Website

Website Future 2024
Website Future 2024 avatar

I originally got the domain name M0INI.radio so that I could have a radio related domain for email.

Since 2017 when the domain was granted by the .radio authority, (you have to prove you have a link to radio or a radio license from a licensing authority), I setup a basic place holder website, and started using the domain for email only.

However, I have now decided, that I will expand the domains usage to also be used for blogging for the station and what I am up to as a radio amateur.

Therefore, during 2024 and onwards, there will be regular posts on the stations website.