antenna trimming?

RG-62/u was used for Arcnet networking,

and IBM 3270 terminal systems:

Ahh, I love the smell of LANtastic over RG62A/U and TCNS in the morning.

You might want to ease up on whatever you're sniffing. Arcnet and

My favorite gizmo was the passive hub. Huge amounts of cash for a mysterious sealed box with 3 or more BNC connectors. I eventually dissected one and was rather disappointed to find only a few resistors.

I'm still not certain that AM/FM car antenna coax cable is RG-62/u. I haven't found a suitable car antenna to compare with the boxes and boxes of RG-62/u I have left over from ripping out Arcnet systems (Lantastic) and replacing them RG-58a/u (Ethernet and Novell).

Whatever. I heard it from some Delco engineers who designed their car radios in the '70s, and saw it on plenty of car radio antenna cables in the '60s & '70s. The Delco engineers explanation was that a whip antenna for AM was used as a voltage probe, and 93 ohm coax had the lowest loss available. That made it easier to match to the tuned RF input. It was also cheap cable with a polypropylene tube to hold the braid and surround the zigzag center conductor. Compare that to a low loss teflon which can cost several dollars a foot.

Sigh. I never bothered to look. I just found a stainless car whip antenna with coax cable attached. The number on the cable is: 5PT3-30C LCN Google couldn't find anything. Both ends are soldered so I can't inspect the guts. The OD is 5.0mm, which is at one end of the range of RG-62a/u jacket diameters of 5.1 to 6.2mm. I would measure the PF/ft, but my destroyed my LCR meter is busted. It probably is RG-62/u but I'm still not convinced.

Well, let's see. The cable is 4.5ft long. ohms pf/ft pF RG-62/u 93 13 58.5 RG-59/u 75 17 76.5 RG-58/u 50 30 135. Yeah, I can see the reason. The input tuning stage would never tune with that much capacitance.

Well, it could be matched to almost anything. However, the low coax capacitance would give the trimmer in the radio a much wider tuning range.

They didn't PTFE when Bill Lear invented the first "Motorola" car radio.

Also, at 1MHz, the difference in cable losses between various dielectrics is zilch at 4.5 ft. They could have used aluminum foil wrapped garden hose, with a coat hanger as center conductor, and gotten the same cable loss.

Well, much of this thread is over my head now, sort of, but ftr, I was

Interesting. For example: Learisms:

# On electronics, "There's only one thing worse than an intermittent, that's an intermittent intermittent." # On weight reduction in the Learjet, "I'd sell my grandmother to save one pound."

In the land mobile biz, it was called Rotomola.

Search Google Patents for "William P. Lear" in order by date:

There were radios fitted to vehicles before Motorola. However, they were big and bulky adaptations of console type radios. Together with the A, B, and C batteries, the radio usually more than one passenger seat. The antenna was usually a square loop about 4ft in diameter. It worked, but I wouldn't exactly call it practical. There are photos on the web, but I'm too lazy to look. By the late 1930's, components had shrunk sufficiently that to make a small radio. What Bill Lear did was make it fit in a package that was small enough to be practical in a car, which included the then unusual minimal rod antenna design.

Here's the original car radio (mounted on the steering column):

Incidentally, many police departments used AM frequencies at the top of the AM broadcast band for dispatch up to the early 1970's. In Smog Angeles, listening to the police on a tweaked AM car radio was common.

I have a toolbox full of coax and OTP/UTP tools.

Thomas Conrad Networking System. We used TC cards for Arcnet in both coax and OTP solutions.

Sounds like it's from one of many un-named Chinese factories that churn out crap that almost works. Also, the RG (Radio Guide) standard was done way with years ago, so even if the cable met the RG/62 specs, it could have a different marking.

So? I never said it did. I was comparing the quality. They continued to use the same RG/62 coax, even when alternatives became available.

Who would use crap like that, when a ready made cable was available COTS? Who would want to screw with trying to route that through a fender, and under the dash? That is the worst straw man I've ever seen.

BTW, I have seen cheap replacement car radio antennas made with RG-58 and they were crap on FM. Of course they were only $3 each by the case of 25 and a lot of half assed installers used them. The shop had a pile of craptennas that were removed to install what belonged on the various cars & trucks we serviced. They would have filled a 55 gallon drum.

The first car radios used an antenna under the running board. There were many changes over the decades.

Do you happen to have any of the TCNS 100Mbit adapters?

Michael

Thomas-Conrad Network -- I am particularly interested in the 100Mbps version and in finding NICs for it (I have an old ad-insertion system that outputs on 100Mbit TCNS and I actually am considering doing 100Mbit over RG69 which was previously laid underground for CATV distribution.

Michael

Unfortunately, no. Haven't seen one since 2001.

My grandparents have a Philco console set from the 1930s that has that police band marked on the dial.

Yeah, that was my reaction at first, too. Later I found it was actually quite useful when taking short "safety naps" at rest stops. A 15 minute nap does wonders when I'm feeling not so alert in the afternoon. 'Course nowadays I just use the alarm clock feature of my cell phone.

Yes, but it was one way communications from the police station to the police cars, and was right above the AM BCB. They used 'Police Call boxes' to contact the dispatcher. They were telephones in locked metal boxes that ran directly to the dispatcher's office.