Batboard

So I've now got the high-split VHF modules in my Saber 3 (which originally had low-split VHF equipment). It "works" in that I can talk between the Saber and another radio on my desk.

However, sensitivity is awful. (I'd wager that the transmit portion needs work too.) A scanner with a stock antenna is picking up all sorts of local signals; the Saber is silent, and just gives a 'pure' rush of static if I open the squelch: it's not hearing anything. (Unless it's right near it.)

Long story short, the radio needs to be aligned. However, the equipment I have to work with is some other radios (including an all-mode rig that will tune in 1 Hz steps, if I needed a more exacting measurement) and a multimeter. I don't own (or have access to) a service monitor, or even much in the way of test equipment (no wattmeter, signal generator, frequency counter, etc...).

Can I do a 'basic' alignment without any fancy equipment? It needn't be perfect, just make the radio usable. Can I do it?

[bWhile alignment on the radio can be performed using 'off the shelf' radios for receive and transmit, the only way to get the task performed properly is with the correct tools.

Use of other radios as the receiver and transmitter is actually a horrible example of an alignment as you can not measure signal strengths, nor sensitivity of the receiver, this will, at best, be a ultra crude approximation of an alignment.

The use of any radio as an alignment 'tool' is the worst possible scenario to use one or more in as they are wholly unsuitable for this task.

Many times, the peformance of the 'tuned' unit can be even worse after an 'alignment' than prior to it as the signal overload from the test radio can cause spurious signals to be peaked upon instead of the actual frequency or frequencies it was intended to tune to.

Harmonics and IMD products can be horrendous in an environment where high power( 1/8-5 watts) can actually degrade the radio requiring the tuning, and therefore, be even far more troublesome to return back to peak perforance should this measure be undertaken.

[/b]

How would I go about fixing poor (awful) receive sensitivity? The oscillator warp setting seems to be about right; I checked it against the discriminator meter on the ham rig in the basement.

I put the frequency of a local paging transmitter into the Saber. It's full-quieting on other HTs, and pegs the meter past S9+60dB using the external stick. The Saber doesn't open squelch, but I can make out that it's there if I use the monitor button.

What would I look at to start to fix this?

Assuming that your reference oscillator IS on frequency, you still have to deal with Tx power out (can't be done with your set up), Tx deviation (can't be done), Antenna VSWR (are you using the original antenna that was for the low split? That will affect Tx AND Rx.). Do these new modules work in another radio or are you guessing that they are good? Your best bet.... get the proper equipment to do the proper job.

I have moved sabers from low to hi split and I never had any troubles like that. It almost sounds like you have something that's broken. Maybe the F.D. Switch near the antenna or the receiver itself.

You need to answer this question to yourself: "Am I going to be doing any radio service work after I get this thing fixed?"

If so, do yourself a favor, and get something that at least approximates the right equipment for the job.

Now, I am biased as all hell - I want you to run right out and buy a fully optioned-out IFR 2975 - because that's what pays my paycheck.

After all, you have $75K to blow on test equipement, right?

Didn't think so.

OK, but maybe you can find an old 1200(A|S|Super), 1000, 1500, 1600, COM-120(A|B|C) on Fleabay. Maybe you find an old Marconi 2944 or 2945, or an old HP-8920 (HP just dropped support for them, and there are a lot of shops liquidating them and going to, well, modesty forbids....)

Hell, even a Ramsey service monitor would be MILES ahead of where you are - and the Ramsey is about $4K new.

Trust me - if you are going to be aligning radios at all, you really should have the right tools for the job.

If you don't - contact your local ham club - maybe one of them has something you can borrow. Maybe your local emergency comms guys have something. Where'd you get the Saber? Maybe they have something?

Really, trying to do the sort of alignment and troubleshooting you want to do without at least a basic RF signal generator with a good attenuator, a basic RF power meter, and a basic deviation meter is like trying to fix a Switch watch with a hammer and a roll of Duct Tape.

But then again, I am both biased as hell and spoiled as hell.

not to mention to properly test/align/tune a Saber requires the RTX4000B text box, factory test cable, sig-gen/svc monitor, service manual, RSS, and computer. If you plan on troubleshooting hardware, you'll also need the test jig which allows you to power the radio outside the housing, etc.

The Saber is one of the most cantankerous radios to align. It can outperform most XTS radios (on analog of course) for RX sensitivity, selectivity, and quality of TX signal, but it also needs a proper alignment by a qualified tech. It isn't as easy as aligning and old crystal radio or 1970's Icom ham rig.

Think of a Saber as a BMW or Porsche of radio, they both require specialized tools and training to properly diagnose, tune and repair them to factory condition.

Sabers are pretty easy to work with. There really is no alignment that will affect the RX except the reference oscillator. This will show up as TX freq error also, easily checked with a freq counter, dont trust the disc meter on the ham rig in the basement. Im with Mancow on this one, something is wrong.

Okay, so let's change my question a little. Cast alignment to the side for now... How (without fancy equipment) could I go about troubleshooting terrible sensitivity?

Transmit is at least very close to on-frequency. As far as receive, I put in (just for receive) the paging transmitter at 152.6000, and also put in 152.5875, 152.605, and the signal is definitely clearest on 152.6000. (FWIW, I was also able to tune it in on my mobile radio, which hasn't had an antenna for close to a year. S9. Something's definitely awry.)

The FDS and the receiver module are properly seated. Next on my agenda is trying to swap the FDS and receiver from a known-good Saber on this split.

If that doesn't work, where else should I look?

Bad FDS. Swapped 'em out and it's working great. As usual, you guys are great.

The FDS looks pretty simplistic, though. How does one go bad?