A quick play with a Marconi 2955B Radio Communications Test Set, very impressed....
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- Опубліковано 25 лис 2020
- Whilst we had a great play with the Marconi 2955B, we probably proved why not to buy a Leixen "25 watt"( or in real life 18w) Handheld. We ended up putting a new lead on the Leixen after our video and yep, its a firmware issue on the radio that we need to chase in the future. Big thumbs up for the Marconi 2955B, big question marks around the Leixen Handhelds for sure. Just as a sidenote, the Leixen may not meet any standards approval with the ACMA so please do not go out and buy one. Our usage of the Leixen is all on dummy load with our scientific license and apart from a couple of isolated experimental applications that I can think of, they may well be deemed illegal to use on an antenna in Australia Cheers brenton vk3cm jdw229 pls subscribe and also feel free to join us on Facebook at Aussie Radio Pickers or vk ham sales and service anytime
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The AF gen output can be used to check signal to noise ratio.
Knock together a BNC to radio MIC lead.
Put the test set into TX Test.
Put the radio into TX.
The radio will get the above signal at the MIC socket and transmit it to the test set.
Because the test set know the frequency and amplitude of the tone it generated, it can measure and display the resultant S/N ratio.
Any decent radio manufacturer will state the signal to noise ratio that the radio can achieve for a given input.
For the lead, I usually butcher a cheap speaker microphone by cutting off the microphone end and terminating in a DIN plug. Separately, I have a small project box with a DIN socket which accepts all my leads, along with two BNC leads, one for AF in and one for AF out (to go to the test set). The box also has a momentary push switch for PTT along with a toggle for longer tests.
That radio is very interesting!
Hi Brenton, interesting comment regarding RF techs having female children. I'm a power linesman working 132kV and over 35 years I've noticed the same in my colleagues!
The selling point when they were introduced was the ability to capture a transmitters ‘signature’ thus allowing forensic proof of wrongdoing.
Great video, I've got a Motorola R2001D (R2010D) here which is playing up, I noticed it intermittently goes off frequency by a few 100hz randomly, it's not the 10MHz reference as I've tested that and also fed in a 10MHz and it still does it. I recapped the PSU's and the CRT boards, re-seated cards and cleaned contacts. But cannot locate the fault. I have a feeling it's the A9 card and I don't have a PCB extension here for the cards so cannot fault find it. So I'm off to buy a Marconi 2955R tomorrow. But I did not realise it does not do SSB! So now I'm not sure what to buy. I'm in the UK and R2001's are extremely rare.
I love your videos! have the 2955B and use it daily. Favorite functions are for quick transmit testing for power-frequency, and receiver testing for sinad and s/n ratio. Works great for old CB's to find which crystals are bad and if the receiver is to spec. When restoring old radios its great for the quick once over to see if the unit is in or out of spec! Maybe do a video with that Lafayette HB600 to measure each channel crystal for frequency and check receiver performance for sinad and s/n ratio to see how close it to .5uv! I have an HB600 I restored and it performs at the .5uv on receive at 12 db sinad and 10db s/n according to the 2955B. Cheers Don
I used to use these for Her Majesty 20+ years ago. You get a lot in a small package. The IEE488 (GPIB) general purpose interface bus allowed most of the functions/inputs/outputs to be controlled auotmatically from a PC. Using a GPIB switching system lots of pieces of test equipment could be linked and switched automaically, signals conrtolled and measurments recorded and even pass/fail reports printed out. However the rise of USB has rendered GPIB obsolete.
I would’ve checked/changed the lead before doing the video 🤔😂
Hope you’ve fixed it
Good information... subscribed 73.
Yours is in nice condition. I love my 2955B its much better than the 2955 and 2955A. The only letdown is the lack of ssb measurement. I use mine for vhf and uhf measurement mostly.
Hi i use a mixer so i can listen to SSB on the 2955, and input the 2955 signal generator to the mixer
And then the lo out of the mixer to the AF input of the 2955,
So you are re inserting the carrier using the mixer and the 2955
Dave Browne 2E0DMB
Only problem i noticed with this unit is the exposed bypass switch relays that controls the input from the connector to the option receiver or to the main unit. The relays are exposed and subjet to get moisture and dirt thus one day they might get stuck when change from receiver to tx mode...
G day from Japan. Your Marconi `s power shows watt and dBm. But my 2955B software version 03 only show watt. I wonder why... What is your version? Regards 73s
That Marconi is a very nice unit. Now I have to find one for myself because my test set was made for working only on CB radios.
My 8 watt Baofeng UV-82HP does only 5.7 watts on high on 2 meters. On 70cm is is barely over 4 watts. So much false advertising with these Chinese radios and they have terrible harmonics. I regret getting it since I could have purchased a Yaesu FT-60 for not much more. Lesson learned!
Are these hard to find?
As a complete amateur I have so many questions. I do physical radio repair but need so much advice on how to properly use this device.
Do you know the standard data(EMF Level) for motorola GP3188?
Maybe it need to be plugged in to a different power source? The radio, to put out full power!
You made some comments about scientific licenses in the description if I’m not mistaken that radio can be used on the ham band do you have a standard or above class license because of the out
.8uV to break squelch?! That's pretty bad.
A modern Motorola DMR handset will break squelch at .2uV
Measuring a spectrally bad radio is easier if you don't use auto tune on the 2955B but instead define the expected frequency, it will then read frequency error and the acquire time is even faster. Not all of the Chinese rigs perform like this one, the most hated one is an order of magnitude better.
18w out of a handheld? Yikes.