Coax from rig/amplifier to antenna

[VK2KPK]

I saw this in the 144MHz amplifier section:

For example I had a ham who had his amplifier constantly tripping.
The problem was a bad piece of coax. I was surprised to hear he used 3 different pieces of coax from the antenna to the amplifier.
This means a heap of connections, losses and points were water can get into the coax.
73 Ron
VK4DD

How do you minimise this given:

Rig/amplifier flexible to outside of "shack", Heliax up the mast, flexible to antenna because of rotator

or even worse:

Rig/amplifier flexible to power meter, flexible to outside of shack, etc as above?

73, Geoff, VK2KPK

[VK2GOM]

Well, the '1 / 2 / 3dB of loss per connector' (select as appropriate depending on source of old wives tale) is a load of rubbish.

A ham member here on VKLogger once got a full bench with literally 100+ military spec connectors of different types, in a real maze across the table. Put a known power in one end, measured the output, and it was little different from the input...

Perhaps if he chimes in, he can elaborate on the test and its results.

I think the main issue is keeping rain at bay with self-amalgamating tape and other good waterproofing practices.

Good quality coaxial connectors are not the problem the urban legends say they are.

73 - Rob VK2GOM / GW0MOH

[VK4AFL]

What surprises me are amateurs who might calculate [or guess ] the transmission line loss but don`t actually confirm it by measurement. For me before I try to work anyone its mandatory to check the loss on a new antenna installation or feedline change. After establishing that the match is ok [anything under 1.5/1 swr is fine by me but some people might want it better] measure the power out at the radio & say set it to 50w. With the same power meter measure the power at the
antenna end. The loss in db is 10.log of the ratio between out & in e.g measuring 42 watts out would be 10. log 42/50.
The log of 42/50 [.84] is .075 x 10 & equates to a cable loss of .75db which would be very good on say 144 MHz but easily
achievable on 50 MHz. I use mostly LDF-550 on 6m with joiners & some 9913 around the rotator for a total [measured] attenuation of .4 db which is not much & one less thing to worry about but there are some systems out there with enough loss to de-ice the coax. 73`s. Trevor, VK4AFL.

[VK2AAH]

Wow Trevor... can't fault your methodology but after you do all that do you still have time to make a contact?

I have a few reasons why I don't do it your way Trevor... first, my arms aren't long enough to operate the PTT while standing at the antenna. Second, I bludge the SiteMaster from work when I need to... so much easier & quicker. And if I insisted on repeating the measurement every time I would operate I definitely would spend a few grand & buy one...

Rob.... thank Heavens you have put that ol' chestnut to bed. Your comment about water is a good one, but another one is the fact that many do not know how to properly terminate a connector- hence the loss. Some here love crimp connectors- I loath them because so many are incorrectly fitted & then assumed to be OK. At least an old fashioned connector can be opened & inspected. Years ago I came across a tech who worked for Philips & I swear he believed that the best connector was the one that used the least amount of parts... I would open his connectors to find half of the "internals" missing!

Cheers

Richard
VK2AAH

[VK4WDM]

properly terminate a connector- hence the loss

Richard, I absolutely agree Many of the problems I had early in my ham life and still have occasionly today are due to poorly fitted connectors, and I have found the same in other people's setups when I have been asked to help sort out a problem. I am still learning after 45 years, I still have difficulty with crimping

My advice is: if you are uncertain how to fit a connector properly then get a skilled person to show you and to check your early efforts. One of the most treaching sessions that a club could run would be one on fitting connectors.

73

Wayne VK4WDM

[VK2AAH]

Hi Wayne,

My problem is that I'm desk bound too much & I don't terminate enough connectors these days. I've become very rusty & with age my eyes aren't as good as they used to be. Practice, practice, practice... nothing can beat it for doing connectors. But we have these wonderful antenna & feeder analysers now that can save us a lot of wasted time & embarrassment if we use them to test our terminations.

Cheers


Richard
VK2AAH

[VK2XSO]

Self Amalgamating Tape Geoff !

An example of a system I do every day. Coax from the transmitter to a filter, then another coax to a bulkhead or flying LDF5 feeder which then goes out through the window and up the tower.
It then changes to another flexible tail at the top of the tower and sometimes via a tower mounted amplifer. Of the thousands of these feeders, very few get water in them or have any significant loss or problems. Self Amalgamating Tape is what it all comes down too.

The equipment is mobile phone base stations. Feeders and DIN connectors, though there are a couple of N types left.
The connectors are done up tight with a spanner. The tighter the connector the better. Though I have found that some N connectors will break if you over tighten them. But that takes considerable effort.

When the connectors are terminated correctly, and tightened then wrapping both of the entire connectors in self amalgamating tape making sure there's no gaps.
The tape is susceptible to UV deterioration of a long period of time so wrapping it in UV resistant electrical tape increases the lifespan.

We use waterpoof glands or bulkhead connectors on feeder windows.
On other small situations I've used drip loops and drip lines. A cable tie with the tail left on the coax provides a place for water to block and drip.

[VK2KPK]

Good information. Thank you.

As a matter of interest what flexible cable does everyone use?

73, Geoff, VK2KPK

[VK3BJM]

Geoff,

That depends on what you can (a) find and (b) afford.

I run separate feeders for Tx and Rx on 144 MHz. The cable around the rotator on the Tx line is FSJ4-50. For the Rx line, it's LMR-400 (it's the standard stuff, not the ultra-flexible version, so the loop is "biggish"). In the case of the Rx line, LMR-400 could be considered overkill, if you have a masthead pre-amp.

Good quality RG213 in a short length would be fine for your purpose at 144 MHz.

If you suddenly decide to start chasing 144 MHz EME, then you can look at picking up a dB or two with improvements in those areas.

In my case, the FSJ4-50 I found at a hamfest a few years ago, so the price was very good (and it tests out A-OK, too!). The LMR-400 was bought new, so was a bit dearer; again, that was a few years ago, but was recently tested and is still good.

Good to work you last night for the first time - yours was a nice signal!

73,
Barry
VK3BJM

[VK2KPK]

The reason for the question is because I have some LDF4-50A courtesy of Alan 3AL. Thanks Alan. I will need flexible cable to get out of the shack to that and then from that flexible cable to the antenna.

This is of course when the mast is erected etc!

ATM it is all a bit Heath Robinson. Running 80W to an 8 element DL6WU type antenna up at about 6m. (Edit: Fed with RG8 type coax with a very short length of RG58 with some ferrite beads.)
Armstrong rotator, hi. Only been on air for a little over a month.

VHF is all new to me so a lot to learn.

Great to work you last night - a new distance record for me!

73, Geoff, VK2KPK.

PS. I have seen Westflex 103 mentioned on the 'net. It seems to be quite good (and cheap!) but does not seem to be available in Aust. Refer g4cqm.www.idnet.com/westlake-pdf/w103-data.pdf

[VK4ABW]

As a matter of interest what flexible cable does everyone use?

73, Geoff, VK2KPK

LMR400 mate. Might as well use the best when using LDF5-50 as the feeder

Gary
VK8AW/VK4ABW

[VK4CZ]

LMR400 mate. Might as well use the best when using LDF5-50 as the feeder

Have to agree Gary! All yagi feeds here are either LDF4-50 (20m/15m/10m/2m/70cm/23cm [also 2/70 dual band vert]) or LDF5-50 (6m) with LMR400 tails on tower .... but a mix of LMR400 and RG213 in the shack

40/75/160 are currently all RG213, will change when the 40m phased vert array goes up requiring 20/40/75/160 to be fed with LDF4-50 via a remote switch box with LMR400 tails!

[VK5TM]

Good afternoon Gentlemen.

Terry VK5TM here, I have just joined the VKLogger forums.

I wonder if you could tell me where to get the Self Amalgamating Tape from please.

Have been out of active ham radio for quite some time and just getting back into the swing of things.

[VK3BJM]

G'day Terry.

There are probably a few options, but most electrical suppliers carry it.

Middendorps, for instance, or Rexel, or Lawrence and Hanson.

Alternatively, sometimes you see it at hamfests. I picked up three rolls of the good Nitto stuff at the Ballarat hamfest, 18 months ago.

73,
Barry
VK3BJM

[VK2XSO]

I'm lucky, I just get mine from the bin at work.
If you see riggers working on a mobile phone tower, just ask them if you can have any stuff like tape left over from the job.
They are often given more than enough cable ties and tape and connectors to do the job with some spare. You may find they have a box of stuff excess that they have been hoarding and
will happily give you.

I use SCF12-50 or FSJ4-50, FSJ2-50 or FSJ1-50 for flexible cables.
If need be I'll lower myself to RG214. It's the same as RG213 but Silver plated Double shield and it turns up at field days pre-terminated with N connectors on each end.

LCF12-50, LDF2-50, LDF4-50 and LDF5-50 for other feeders.
I'm just spoilt for heliax and could no longer lower myself to those braided coaxes
Even RG6U has been replaced with LDF1-75.

[VK5TM]

Thankyou Sir's.

I have an account I haven't used in ages with P&R Electrical, so will try them.

Re telco techs etc, I live in the middle of nowhere, so never get to see anybody like that, but will store that info just in case I do.

Terry VK5TM

[VK2KPK]

Thank you. Time to find some 'net suppliers - I too am in the middle of the bondoo.

73, Geoff, VK2KPK

[VK5BI]

Terry, all the P&R branches stock the tape.

Cabac, SAT1 is the cat no.

Regards

Wayne VK5BI and P&R employee

[VK5TM]

Thanks Wayne.

Which store are you in? Might drop by if in the area at some stage.

Terry

[VK4BLP]

There's also the Star brite brand Liquid Electrical Tape, that can be got from boat chandlers and the like.

You just brush it on, and let it dry.

About $12 for a 166ml tin with brush in the cap.