Amstrad Mobile Antenna Whip Length.

[The Collector]

As above, I'm trying to find out the length of the original whip that fits in the old red-based and branded Amstrad aerial if anyone has one in their collection please?

I have a 5ft whip from another aerial that I'm willing to cut down to length (about 3ft if memory serves me correctly), but it'd be nice to know the exact length to save me faffing around

I could use a piece of copper wire and chop that down bit by bit until I get a good swr length and then cut the whip to that size, but again, it's quicker just to ask first.


Cheers.

[The Collector]

Length now found off-site. Thanks.

Mod's can delete this post now

[lambrettadave]

Hi Dave as soon as I find my tape measure I will let you know how long mine is.
Ps mine was a splittable whip.

[The Collector]

Hi Dave.

Bigpimp measured his boxed/carded one for me so I know the length of the 2 pieces if whip. However, if you can let me know if the whip connector piece separates the two pieces of whip inside it (if they don't actually come/touch together), that'd be handy as if they don't, it increases the length a touch.

Cheers.

[lambrettadave]

The bottom part of the antenna has a join in it with a grub screw to fasten the top section to it.
Total length of mine is 125cm

[The Collector]

Cheers Dave.

I'll get the hacksaw out the weekend (or grinder if I'm feeling lazy) and cut the whip I have to length.

[lambrettadave]

You may want to leave about 10 cm extra as mine didn't swr very well

[The Collector]

I'll swr it with a length of wire and transfer the length to the whip once at the right length.

Because it's on an aftermarket magmount, I'd prefer not to cut it exactly to length, just in case it makes any difference at all.

It gives me a starting point though so thanks again.

[ChrisMagpie]

I'll swr it with a length of wire and transfer the length to the whip once at the right length.

Nooo!! Don't do it! The length in copper will be shorter than the length needed in stainless steel, so if you transfer the measurement over, you'll chop too much off of the whip

[The Collector]

Are you saying that a copper whip would be shorter than an stainless whip needs to be to get the same swr? Never heard of that before...although I reckon copper's a better conductor.

If I make a copper Sigma 4, would it be much shorter than the aluminium version then???

I've got a 5ft stainless whip to use, so I'll chop off just an inch at a time from that until it swr's decently. Or I could just use Dave's measurement and add an inch to be safe if he reckons it doesn't swr in very well.

You learn something new every day

[ChrisMagpie]

Are you saying that a copper whip would be shorter than an stainless whip needs to be to get the same swr? Never heard of that before...although I reckon copper's a better conductor.

It's true! Page 22 of Lou Franklin's Screwdriver Expert's Guide:
(Discussing 102" whips)

. . . have you ever noticed that fiberglass whips are shorter than steel whips? They're 96", to be exact. Reason: The fiberglass whip is essentially a copper wire embedded in fiberglass; in other words, a "copper whip." Your CB radio is generating radio waves at the rate of 27 million times per second. But even at this incredible speed, it still takes a definite amount of time for the radio wave to travel from one end of the whip to the other end. Since copper is a much better conductor of electricity than steel, the same wave shoots through the copper much faster. So in other words, the fiberglass-copper whip doesn't have to be as long for ¼ wave of the CB signal to "fit" on the whip. Technically, this is called "propagation delay." But both types perform equally well.

Lou Franklin = childhood hero!

If I make a copper Sigma 4, would it be much shorter than the aluminium version then???

The idea that you're going to make a copper Sigma 4 the size of your Antron is pushing it a bit!

I've got a 5ft stainless whip to use, so I'll chop off just an inch at a time from that until it swr's decently. Or I could just use Dave's measurement and add an inch to be safe if he reckons it doesn't swr in very well.

An inch at a time is a lot to chop off! I'd be chopping off a quarter of an inch at a time. How about taking SWR readings over six blocks of 40 as you prune, to get more of an idea of how much the SWR is changing with each pollarding event?

We're all trying to save you from that "oh crumbs!" moment, when you realise you've chopped too much off!

[The Collector]

I've done that before now...not with a whip but with wood.
Thanks Chris, very handy info. As you probably know, I'm not into the tech-side of CB. I've got a couple of sidebanders I can fire up to get it to size more accurately.

The 80's "Armstrong" mobile aerials had a stainless whip that was copper-plated. I wonder if that meant the whips ended up a tad shorter than if bare?
I missed out on one about 2yrs ago. It only sold for £3.40 on ebay plus P&P in amongst some other CB rubbish. I forgot to set a reminder and didn't bid. Gutted!

[ChrisMagpie]

The 80's "Armstrong" mobile aerials had a stainless whip that was copper-plated. I wonder if that meant the whips ended up a tad shorter than if bare?

Possibly! As the signal travels on the outer surface. Skin effect, innit?! I'm not much of a techie either though, really
If the twig looks like it's made out of copper, you'd need a Selmar car alarm to protect it!

Maybe this is your "get out of jail" card. If you chop too much off of the whip, you could always copper plate it, to bring the SWR down. If the SWR is still too high, you could maybe silver plate on top of the copper

I missed out on one about 2yrs ago. It only sold for £3.40 on ebay plus P&P in amongst some other CB rubbish. I forgot to set a reminder and didn't bid. Gutted!

We always remember what we missed out on, but don't always remember what we've bought!

[The Collector]

Too true....Midland 76-300 homebase (sold for only £26), wrongly titled Astatic 575-M6 (sold for about £20), job lot of crap with Megatracker 1100 ukfm radio (sold for £23), boxed and mint Transcomm 9000 ukfm radio (24-ish) .....boo hoo
I don't trust those 3rd party sniping tools though as you have to put your ebay password etc in them, so I've missed out on quite a few bargains over the years after forgetting to set an alarm.

[ChrisMagpie]

Shame about that Midland homebase!!
I remember missing a NOS Commtron VIII, which went for peanuts. I got the last day of the auction wrong
Oh well, I didn't *need* it anyway . . .
There's no way I would trust one of those 3rd party sniping tools, either.
I remember sniping success in the dialup days was hitting the button with 43 seconds left to go