Replacing a radio questions

[shajen]

Hi all
bit of a question on radios. Ive had no experience with changing any instruments around. My current single frequency micro air radio seems to have an intermittent fault. Has been bench tested and found to be ok, but it isn’t. 
I intend upgrading my complete radio, Mgl v16 do sound quite good. But i want to know if I buy the radio will, or can, any radio tech fit it?  Do they prefer to buy radios for you so they can get the markup on them? Do most of them have their own preferences, therefore if you give them a radio might they not want to fit it?
Because of the static I’m getting and this intermittent fault I think I may need to start from scratch and replace all the wiring to make sure everything’s grounded properly and shielded properly.   Guess i may need to get new aerial also. Is this a bit of overkill? But if I don’t replace everything I may still have unreadable transmissions.
any thoughts, please?

 

 

[RFguy]

fault find logically.

 

First.....do you have another radio , portable or another aircraft on site that you can test with ?

 

glen

 

 

[shajen]

RFguy , yes it should be logical, but doesn’t seem to be.  We have a hand held that Shane uses to check my radio before each flight. About 50% of the time he reads 4 to 5 on first tx. Sometimes he can’t read me at all so I’ll jiggle around headset, ppt, intercom etc and try again, usually can get it a bit better. In the air though, I’m never sure if someone’s reading me or not. There’s been times when I’ve asked several questions from other acft, no answer, and when I see them on the ground to check , they say they didn’t hear any of my tx. Another friend is often up at same time as me and he always reads 4 to 5.

shane and I have checked the earthing, looseness of screws etc, and a radio tech has fixed wiring on passenger intercom, checked radio in and out of acft and can’t find fault. So seems to be perfect sometimes. I do seem to be able to rd most transmissions ok. Still can’t understand all the Chinese ones though.

my microair radio is in a kit built 20 year old Jabiru, and part of the reasoning for upgrading. Is that I feel if I want to use Class E airspace I will need a better radio and one that can monitor 2nd frequency 

[RFguy]

first thing, dont get too close with your test radio, most portables (and some fixed)  will saturate, and you will hear carrier, but no modulation if too close, so minimum distance 30 meters I'd suggest.

 

Your description does not sound like a radio problem, more a system problem..

 

what do you mean "Still can’t understand all the Chinese ones though.". The chinese radios, are for the 99% part, complete rubbish, the chinese know nothing about audio. u get what you pay for.

 

First question

do you always hear other transmission about as well as expected  , IE hear them well close, hear them scratchy when airborne operating 40-50 miles away ?

 

which antenna are you using, the one in the tail ?

 

glen

 

 

 

 

 

"

Edited April 16, 2021 by RFguy

[shajen]

Glen, apologies, was trying for a joke re Chinese ... ie they never know which direction they are and are always number one! Not their actual radios😀

yes the antennae is in the tail.  Can usually hear aircraft ok, about 3, so readable for most. Although the few times I’ve contacted melb centre they have been quite scratchy and unreadable. Aircraft close by I seem able to read better.

[mkennard]

My radio isn't great first thing, for me if the battery is low the Jabiru doesn't provide enough power.

[Roscoe]

1 hour ago, mkennard said:

My radio isn't great first thing, for me if the battery is low the Jabiru doesn't provide enough power.

And Shajen, what does the voltmeter do when you press the mic switch

and

Do you have same problem with engine off?

[mkennard]

Haven't tried that since I now have a solar panel plugged into the plane in the hanger. Maybe I should test it since winter is coming and the Jabiru isn't great to start in the cold.

 

[Roscoe]

50 minutes ago, mkennard said:

Haven't tried that since I now have a solar panel plugged into the plane in the hanger. Maybe I should test it since winter is coming and the Jabiru isn't great to start in the cold.

 

Yes I have a similar solar system in my Hangar.

My question was to Shajen, so Shajen if you care to pm me, I am happy to discuss your issues on the phone, as I have had similar experience in earlier times with my Jab Radio., since resolved.

[RFguy]

Shajen
OK hmmm. alright. more questions.
1) you said "Although the few times I’ve contacted melb centre they have been quite scratchy and unreadable"

Were you on the right frequency and good line of site to the central base station at the time ?

 

2) you said "Can usually hear aircraft ok, about 3, so readable for most. "

is that 3 aircraft, or on average readability 3 even when they are close ?

 

3) do you ever hear other same aerodrome aircraft readibility 5 or your mate on the portable radio readibility 5 ??

 

 

 

 

 

[pmccarthy]

The symptoms are the same as I had with a Microair some years back, there was slight contact in the soldered joint in the antenna connector.

[RFguy]

BNC sockets which are on flexible chassis onto PCBs are notorious for cracking the solder joint.

 

Almost all the ones I have examined have cracked solder joints.

easy to fix. just takes time to get it apart.

 

even worse possibility, a tech that shoudl know better pushing an N male onto the BNC socket- it fits but splays the inner contacs and it becomes forever intermittant.

 

[shajen]

Been playing around with it today.  So , generally aircraft 10nm or more away readability around 3, quite ok, with occasional interference. Closer they are is really great, usually readability 5. There are lots of high hills around here so perhaps that’s why melb wasn’t readable, also 80nm away, and I think I was only about 4500ft.

RFguy, we found a bare wire that’s been damaged somehow going to the aerial. Taped that up and checked all electrics with engine running. Shane used the hand held and a friend checked with his aircraft at other end of strip. Think we have narrowed it down now, everything’s fine until the transponder is switched on. Nothing else appears to affect the radio much. We have taken transponder out now.

tomorrow I’m going to Benalla so will check with a few different aircraft. 
so getting there😀

[RFguy]

OK, good progress. the bare wire doesnt sound like much...
but a bare wired taped up?   if it was the outer shield of the coax (what is ?) that's fine, doesnt matter . if it was the inner of the coax, that's a problem. it should not be visible anywhere except the bottom of the antenna base...

Photos are useful.  
So you turn the transponder on and trouble. Most older transponders will suck about 1 amp when they are turned on, usually up to 50% more than that on warm up. maybe you have a low voltage due to high resistance in the radio harness. 1 amp is not much though. maybe the transponder is sick and drawing alot more current. KT74s from memory have 2 or 3A fuses in them. I have some cannot remember, have fixed a few. if the HV generator fails, they can draw lots of current.

What model Transponder ? 

 

 

[shajen]

RT459a