RF safety? What’s that? WMBM-AM’s tower.

No no of course not, you can’t burn things with RF unless they’re inside the microwave.

Presenting WMBM-AM, Miami Beach, Florida.

The tower stands in a courtyard behind Radio Bar. The courtyard is fully enclosed. Except…….. The bar uses it as an entrance and exit and storage area and leaves it open to the public.

Sorry for blur in these images, I was unable to stop laughing.

image

Pretty hallway.

image

To the right just inside.

image

To the left just inside.

Note that this tower is not on insulators. It is [barely – see below] grounded. The transmitter output goes to a three wire skirt that starts well up out of reach and is fed by, uh, let’s visit that later

image

Kinda sorta ground. One small wire, about 6 gauge.

image

See that red square? That’s the transmitter output. Right there. It’s like seven feet up in that corner. You can see the two pipes in the photo above. Only a chain and defaced warning sign (not even a standard RF exposure warning sign) separate bar guests and that.

image

Possibly remains of an older feed to the tower…. even more exposed.

image

image

No, the tower lights don’t work.

image

Dafuq?!

image

This has apparently been how it’s stood for years.

On a side note, here’s an at&t installation. The old vault is on a berm above ground to protect it from storm surge. The VRAD, used to supply PooVerse I mean UVerse television, internet, and kind of sort of phone, not so much.

image

You’re, uh, welcome.

The Harris Quest FM

I could write volumes on how awful and ridiculous this box is, but… Here, I summarized it in one image: if you add thick eyebrows, a moustache, and a goatee to it, it looks every bit as malevolently untrustworthy as it truly is. They’ve been out of production for a long time (cheers were probably heard all over Quincy when the order to discontinue them was made) and certain key parts are looooong gone.

image

Cool ferroresonant power supply though.

The fix for easily moved radio knobs

First off, our radio knobs were too easy to turn, causing them to get unexpectedly muted or knocked off channel.

Second, I fail so hard at shitposting. I always want to just fire up WordPress and drop a useless shitpost on here then I think of something actually useful and informative. What follows is a failure to shitpost.

I’m still not exactly calling this a great post because I’m too lazy to edit the images.

Step one: pull the knobs off. Pull straight up. The knob may be tight on the shaft, just don’t apply excessive force in any direction if it is. Be patient. On this Hytera it was pretty easy to pop off.

image

The recess here is what we’ll be modifying. Cut two little circles out of craft foam, mouse pad, inner tube… Whatever rubbery thing you have handy… Or use rubber o rings. It don’t matter.

image

If there’s no hole in them yet, fold in half and cut a slit.

image

Press it down the shaft and all the way into the recess.

image

Reinstall the knob. Test to see that it moves and has more resistance. If there’s no effect, add another layer. If it doesn’t fit back on there, remove it and try a thinner material.

This took me about two minutes per radio I did it on and eliminates annoyance like nobody’s business.

The first time I did this mod was on a Baofeng, so I’m gonna add the shitpost tag. You’re welcome.

Harris Z power supply rectifier notes.

For future reference to myself and everyone else, so I don’t have to keep searching my email every freaking time:

On the Harris Z series transmitters, the SCRs used on the rectifier board may be either one of two kinds. They may be a current part made by Littelfuse or a discontinued one made by (this has escaped my memory banks, sorry!)

If you have the newer board, you have Littelfuse S6055R SCRs on it. If you have the older board, your SCRs can be replaced with the S6055R. If you’re me, you replace them with the S8055R, which is the same part in every way EXCEPT that it can handle 800V reverse voltage instead of 600. (Probably comes in handy in avoiding blowout during power surges?)

Here’s yer SCR.

Troubleshooting: You will receive fault code PSx_TAPy where x is the power supply number and y is the tap number. Try clearing this fault as it may be set by a voltage transient. If it recurs in the same place, disconnect ALL power to the transmitter and pull out the power supply drawer from the bottom. You will need a second person’s assistance. I found it easiest after removing the blower from the back as well. Test each fuse on the rectifier board identified by the fault. If you find blown fuses, change them and try again. If you find fuseholders that look like they’ve been hot, change them.

However, if the fault persists and the fuses and holders are all good, change the SCRs. Using a vacuum desoldering iron will help a lot. I used my Hakko 808.

Voila….. no more jet turbine mode. 😉

Maybe it wasn’t a typo?

A while back I spotted this.

image

image

Imagine my surprise seeing the package has been redesigned and still says the same thing about the vswr!

I’m now officially recommending this antenna for all deployments of Harris Stingray units, Bluetooth spammers, over modulated pirate FM’s advertising strip clubs, and iHeartMedia stations.

The oddball embedded spectrum analyzer

It’s no secret, the Technicolor home cable gateway sucks. However…. if you have one, try http://10.0.0.10:8080 in Chrome or Safari…. (Link will just error if there’s nothing there).

Voila— you have your very own 21st century Graph Channel.

There’s a RF spectrum analyzer in there. Now, it’s not a GREAT one, the minimum frequency resolution is a big wide 6 megacycle wide sweep…. but it’s there.

cable-specOverall view, you can see the bands used for upstream and downstream, divided by a blank band around 100.

That band has some spiky bits in it. What are they? Well… I live within walking distance for the transmitters for a couple of 100KW ERP FM’s…

ENHANCE! There’s 93.5 “The Bull” W228BV-FX; 106.7 WDXJ-FM + HD, 105.9 WBGG-FM, and a few others, all leaking into the cable system at fairly harmless looking levels. I suspect Comcast simply leaves this band of spectrum empty on their cable system to make life easier in the face of RF leakage. (??)

spec-fm-band

I’ll code a GUI interface in Visual Basic…
The view goes in just enough to make the analog carrier and HD sidebands of WXDJ-FM visible and distinct. It looks like the lower one MIGHT be suppressed a bit – this is an interference mitigation feature present in modern HD exciter firmware from Harris/GatesAir, Broadcast Electronics, and Nautel. You can back it down a bit to be all cool and avoid adjacent channel interference.

cable-iboc
I dunno — you can’t expect a spectrum analyzer built into cost engineered nasty home internet CPE to be the best thing ever, but it’s still fun to play with.

What, does it vibrate?

Waaaaaait for it——–
It's IP67 rated in case you drop it over the side of the Love Boat.

 

I wonder if the Tytera MD-390 will have fixed some of the oddball bugs from the MD-380? One notorious one that’s come to light recently is that if you un-key then key up again shortly afterwards, the radio’s transmitter timing slips and it’ll scribble over the opposite timeslot. Sounds like a show stopping bug and I’ve seen it blamed on a bug in the Texas Instruments DSP chip at the heart of the radio, which… I’m not inclined to believe.

Either way, even if it was, it’s not like there haven’t been software workarounds to hardware bugs that work successfully before. Just look at the Linux kernel – it’s got a LOT of fixes for CPU/chipset issues which would otherwise be show stoppers.

All Hail the Bowelfunk

HeartlandPrairie1139notusingconstructionbarHATERS GONNA HATE

SLATER’S GONNA SLATE

I always wished I could hang out at The Max after school, but I never would be able to trust myself not to walk into those railings you see on the left. Dear Eris that looks painful. #fnord
I always wished I could hang out at The Max after school, but I never would be able to trust myself not to walk into those railings you see on the left. Dear Eris that looks painful. #fnord

 

This wonderful chart just showed up from the November issue of QST, confirming in a good size statistical sampling what I’ve suspected for quite some time:

Baofengs are rubbish.

Click to view full size.
Image from the QST article. Apologies to the ARRL for reposting part of their article without permission… but at this point, we just need to stop buying Baofengs and this illustrates the fact well.

 

 

 

 

 

 

This is kinda nothing new. On the first model they sent over here, the UV-3R, rumors surfaced early on that the antenna was critical. The antenna’s bandwidth limitations were being used as a harmonic/spurious emission filter. If you used a third party antenna, especially one that’s very broadband like a discone, it’d spew. The UV-5R’s are everywhere now and well, aside from you having about a 70% chance the radio works at all, there’s about a 50% chance it has spurious emissions exceeding FCC standards.

 

Beautiful.

 

You will notice if you look at the chart above that a small sampling (as in, ONE unit each) of Kenwood and Yaesu radios also failed to pass, but I get the feeling those were radios that had soaked up a bit too much puddle water in their years. We hams tend to keep our rigs till they turn to once expensive dust….. then claim they’re STILL wurf way the hell too much.

I think I may still have one UV-5R kicking around somewhere. I haven’t used it in nigh forever, because the last time I did, the receiver started going deaf and shutting down with a crackling sound whenever you moved the radio. It wasn’t a cracked solder joint at the antenna connector (a VERY common problem, historically, on almost all brands of handheld radios). The board was just plain goin’. Either way, after reading this, I’m declaring it to be a [lackluster] receiver only.

At work there’s an ever shrinking bundle of Baofeng/Pofung 888 single band radios that were obtained out of desperation as the old Motorola CP200’s and newer CP185’s all gradually started to fail. They just plain don’t work right. They drift in frequency in mid transmission, emit strange noises, go weak on transmit, or fail to receive. On a side note – funny how the CP200’s lasted over a decade and the CP185’s, now made in China, barely make it beyond three years’ service. I wonder who “Motorola” actually buys them from? Bueller? Bueller? *squelch*

 

Apparently in the 2012 tests, some TYT radios showed up with half of the small sample being bad – interesting to note that they’ve never reappeared. The TYT [Tytera] MD-380 analog/DMR radio is starting to gain a lot of use lately, hopefully they’ve cleaned up their act!

On a side note, boy, Tytera sure never seemed to use their full name OR the same exact font that Hytera uses for their logo until Hytera started really kicking butt with their DMR line. Gee I wonder why they just happened to jump to similar trade dress. 😉

(Comparing the looks of the MD380 to the looks of a Hytera radio, however, is like comparing the looks of a Samsung Galaxy S6 with one of those toy plastic cellphones that’s full of candy.)

1 2 3 4 5 6 8