Amazing Power of Good Antennas

[Dockhead]

Originally Posted by s/v Jedi

Insertion loss of connectors, crimp and solder connections are important too. It's not easy to get right but when it is, it's a thing of beauty VHF transmitter- and antenna design is what got me to study electronics.

I pulled fat RG213/U cable all the way to my nav table from the masthead, so the only insertion losses are one set of Type "N" connectors at the antenna, and the PL259 which connects to the Icom M604 radio.

I did away with the traditional connectors at the base of the mast -- I figure that if I have my mast out only every 10 years or so anyway, I'll just hack off and replace the cable every time, anyway. The old cable had BNC connectors there which had corroded from rainwater coming down the mast

[Dockhead]

Originally Posted by Cormorant

I've been wanting to upgrade our VHF antenna, which is currently on our cabintop and not very effective. Trouble is, our mast is in a tabernacle and we frequently fold it down for trailering or to pass under bridges. I could mount a Galaxy at the masthead and run RG213 down inside the hollow mast . . . but I would need a weatherproof quick-disconnect at the base. Does such a thing exist?

Type "N" connectors. Not only weatherproof, but much lower insertion loss ("impedance bump") than UHF connectors (PL259/SO239). If it's outdoors, you will still want to wrap it with self-amalgamating tape, however, to be absolutely sure water doesn't get in.

[Dockhead]

Originally Posted by colemj

I am betting that the majority of your improved performance came from the new higher quality cable and connectors you installed and not the antenna.

Mark

We'll never know for sure, since I replaced cable, connectors, and antenna at the same time. Poor experimental procedure, but I had no choice since I only had the mast down once.

I have a hunch, however, that the antenna really does make a big difference. It is a dipole made of silver-plated elements. Being a dipole, it doesn't need any ground plane at all. Whip antennas are designed with car bodies in mind -- using the steel trunk lid or roof as the ground plane. I doubt that the masthead truck really works properly for that.

But that's just my extremely amateurish radio-engineering guesswork, not worth much. Maybe Bill Trayfors could weigh in with a more weighty opinion.

[goboatingnow]

Originally Posted by Dockhead

Type "N" connectors. Not only weatherproof, but much lower insertion loss ("impedance bump") than UHF connectors (PL259/SO239). If it's outdoors, you will still want to wrap it with self-amalgamating tape, however, to be absolutely sure water doesn't get in.

I prefer proper IP67/68 fittings and I dont use any type of tape, I find tape just acts as a water trap.


IP67 for splash IP68 for submerge risk ( deck etc)
Dave

[neilpride]

In the rigging shop we use a thin coat of lanocote and a piece of heat shrink..

[s/v Jedi]

Time for you guys to buy a roll of silicone rescue tape and find out for yourself

[Paul Elliott]

Originally Posted by S/V Illusion

The efficacy of any antenna is measured on it's ability to radiate efficiently.

Any antenna can be made to radiate efficiently.

Therefore, any antenna can be "good"

I'm not following you.

Some antennas are less efficient because of loading coil losses, too-narrow bandwidth, or surface corrosion, etc. Some of these issues can't be fixed, and will result in poorer performance. We don't usually use a tuner for VHF antennas, so the bandwidth and design-frequency factors can't be tuned away.

[Dockhead]

Originally Posted by s/v Jedi

Time for you guys to buy a roll of silicone rescue tape and find out for yourself

Self-amalgamating tape "rescue tape" wrapped with elec tape is "best practice", AFSIK. Used by telecomm companies; called a telecomm wrap.

[Teknav]

Doggone it! Don't you guys miss the " coat hanger wire antenna" solution?

Mauritz
Going to behave now!

[Rhapsody-NS27]

Originally Posted by Teknav

Doggone it! Don't you guys miss the " coat hanger wire antenna" solution?

Mauritz
Going to behave now!

I got something like that for a simple VHF verticle.

It's the back up to the back up to the back up.

[El Rubio]

There's quite a bit of hair splitting regarding antenna line/cable losses and their actual affect on real life operating. For example, I often recommend LMR240 over LMR400 or RG213 in most installations because the difference in loss is negligible and almost totally imperceivable. One poster here said he ran "fat" RG213. 213 is great for VHF, but "fat" is the key term here. If he pulled 100', then he saved 0.2dB of loss over 1/4 inch LMR240. The 240 would probably have been significantly easier to route to the radio.

N connectors were designed to be weatherproof, but not very well. If it's exposed, it WILL get wet. You never see commercial operators use N connectors that aren't sealed. If you think sealing with various tapes "traps water", you're not doing it right and possibly unnecessarily spending more money for water proof connectors. At VHF frequencies, the insertion loss of N type connectors is so miniscule and similar to PL259's, that it isn't worth noting. N's are typically made better, but even the cheap PL-259's are effective and low loss when installed properly. The advantage of N's appears at UHF freq's.

My point is, that the average non-engineer reading this thread and planning a VHF installation might spend $$$ & extra work to save fractions of losses, that are insignificant in real world applications. I'm not denying that less loss=better signal, but in situations where the difference is <2 or 3dB, it may not be worth the effort and expense for minimal performance improvement.

[goboatingnow]

Originally Posted by El Rubio

There's quite a bit of hair splitting regarding antenna line/cable losses and their actual affect on real life operating. For example, I often recommend LMR240 over LMR400 or RG213 in most installations because the difference in loss is negligible and almost totally imperceivable. One poster here said he ran "fat" RG213. 213 is great for VHF, but "fat" is the key term here. If he pulled 100', then he saved 0.2dB of loss over 1/4 inch LMR240. The 240 would probably have been significantly easier to route to the radio.

N connectors were designed to be weatherproof, but not very well. If it's exposed, it WILL get wet. You never see commercial operators use N connectors that aren't sealed. If you think sealing with various tapes "traps water", you're not doing it right and possibly unnecessarily spending more money for water proof connectors. At VHF frequencies, the insertion loss of N type connectors is so miniscule and similar to PL259's, that it isn't worth noting. N's are typically made better, but even the cheap PL-259's are effective and low loss when installed properly. The advantage of N's appears at UHF freq's.

My point is, that the average non-engineer reading this thread and planning a VHF installation might spend $$$ & extra work to save fractions of losses, that are insignificant in real world applications. I'm not denying that less loss=better signal, but in situations where the difference is <2 or 3dB, it may not be worth the effort and expense for minimal performance improvement.

I agree with most things here except tape. I use Bulgins connectors , the design doesn't need or suit tape, I've open more self amalgamating taped connectors which had water inside , primarily because the tape to cable joint Is hard to maintain


Would completely agree with cable and pl259s etc. good quality connections are what count not the cable and connector

For connector setups that arnt inherently waterproof , then there no other option
Dave

[btrayfors]

I agree with most of the above, except that a loss of 3db = a 50% loss of power.

A VHF radio putting out 25 watts with an antenna system having a 3db loss would have an ERP (effective radiated power) of only 12.5 watts.

That's significant, in my view.

Maybe El Rubio meant "<0.2db or 0.3db" ???

Bill

[El Rubio]

Originally Posted by btrayfors

I agree with most of the above, except that a loss of 3db = a 50% loss of power.

A VHF radio putting out 25 watts with an antenna system having a 3db loss would have an ERP (effective radiated power) of only 12.5 watts.

That's significant, in my view.

Maybe El Rubio meant "<0.2db or 0.3db" ???

Bill

You read it correctly. My point is a 2-3 dB change isn't as significant as what 1/2 power is perceived to be. From the perspective of a distant receiver, the 3dB change is minimal. A 2dB change is hardly detectable by ear. Fretting about tenths of a dB insertion loss or buying expensive cable & connectors is not necessary at VHF frequencies.

[btrayfors]

Originally Posted by El Rubio

You read it correctly. My point is a 2-3 dB change isn't as significant as what 1/2 power is perceived to be. From the perspective of a distant receiver, the 3dB change is minimal. A 2dB change is hardly detectable by ear. Fretting about tenths of a dB insertion loss or buying expensive cable & connectors is not necessary at VHF frequencies.

Well, then, we do not agree.

While I certainly agree that fretting over insertion loss of connectors (essentially negligible if installed correctly) is silly, I cannot agree that a 50% loss of radiated power is insignificant....at VHF or HF or MF or even UHF frequencies.

At the fringes of reception area, it may make the difference between capture and no-capture for VHF/FM, or between intelligible and non-intelligible voice with the squelch open....as in an emergency situation.

Small point, perhaps, but I don't think it's a good idea to give up 1/2 of whatever power output you have available because of an inferior installation.

Sorry, but more than 50 years of hamming and many years of boating and professional radio installation, testing, and certification make me just a bit cautious about throwing power away.

Bill