Feed-LIne Loss and M&P Coax
This is a multi-phase project with phase one moving my shack from the large room it was in to one of the front bedrooms in the house. This was a huge under taking as pulling 1/2 hard line out of the room and back into the attic and rerouting it was hard enough, but with 4 - 7/8 inch and 2 - 1 5/8 and 1 - 2 1/4 hard line runs were hell. It took Ruth and I almost a week to pull and route hard line into the new room.
The 2nd phase is designing the shack to fit in the smaller room, plus a great deal of advanced automation. With the ability to operate my entire shack via my cell phone or tablet, including switching antennas, rotating antennas, activating amps, etc.
This has greatly extended the duration of the new shack project, due to trouble shooting and fine tuning the automation. Plus a couple of times, we assumed it was a bug or issue within the automation and we spent time chasing a bug that turned out to be an old technology hardware issue….Such as the recent hard line connector failure.
PHASE 3 is the upgrade of the antenna system with a large H-Frame going up to support a full stacked array of antennas, plus an RAZER Antenna elevator system with electric wench that can be raised and lowered remotely.
And now with that project, comes the topic of today’s BLOG.
COAX FEED LINE LOSS.
As everyone who has ever come into contact with me understands I am FANATICAL about feed line losses.
With the changes on the tower, automatic relay switching, pre-amps and the Elevator, I am looking at 8 - 25ft low loss rotor jumpers from the antenna to the top of the tower for the hard line connection.
In the past I have always used LMR-600 Ultra-Flex, Jerry KB2WDM has really been a huge promoter of the new Italian Messi & Paoloni Coax, so I thought I would give it a try out and see how it performs.
I honestly have to admit, that I am more or less impressed with it, and I especially like the connectors that they provide for this specialized cable.
It is EXTREMELY FLEXIBLE AND provides good low loss, specially on the shorter runs so that it is perfect for the jumpers between the antennas and the hard line and with the excellent flexibility it works very well for the rotor loop at the top of the tower.
I purchased a 100ft of it, to do some side by side real world performance test, and in a fashion that would allow the novice Amateur to the experienced to understand exactly the impact that the different coax feed-lines can have on your signal.
For our testing purposes we will focus on 2 meters at the Single Side Band calling frequency of 144.200 and will use 100 Watts as our base power injection.
For our test, we have set up equal lengths of Feed-line RG-58, RG 213, LMR 400, LMR 600, UltraFlex 13/.500, 1/2 hard line, 7/8 hard line and 1 1/4 hard line.
A FM Transmitter putting out 100 Watts into the head-in of the feed-line with a Motorola watt meter, and a dummy load rated to 1000 MHz. The SWR with the dummy load and watt meter is a clean 1.1 SWR.
The 100 watts is fed into the 100ft length of coax and with the exception of the RG-58 and RG 213, N connectors are used.
Coax Type: Watt Reading Loss % Note:
======================================================================
Belden RG-58 33 Watts 67% Used this as a joke
Beldon RG-213U 53 Watts 46%
LMR 400 69 Watts 30% What most people use for low loss
LMR 600 79 Watts 21% My normal go to for rotor jumpers
M&P Ultra-Flex 500 82 Watts 18% Extremely flexible
Andrew 1/2 82 watts 18%
Andrew 7/8 89 Watts 10%
Andrew 1 1/4 92 Watts 7%
As you can see the M&P Ultra-flex 500 performed very well, plus it has the advantage of being extremely flexible. I believe the quality of the connectors that is designed for this cable plays a bit roll in the loss levels. They are extremely high quality.
On all future projects, I will be using the M&P UltraFlex 13/.500 feed line for my rotor jumpers at the top of the tower, combined with the lengths of under 30ft in all most all applications the loss is very low and will not impact my performance.
NOW A VERY IMPORTANT FOOT NOTE: Keep in mind the loss you are seeing in the cable and equate that to not just your transmit but your receive as well and invasion.
So imagine that weak signal you want to hear, if you take 30% of the signal strength away with feed line loss…..
Looking at this chart, you can understand why I place so much importance upon Feed-Line loss.
Introduction to 1296 Operating
Introduction to 1296 MHz Mobile Communications
Mobile operation at 1.2 GHz offers some unique advantages and challenges. Let's take a look at some of the details.
Simplex communications at 1296 MHz FM differs somewhat from regular two meter simplex operations.
Usually, for two meter simplex operations, one would try to use gain mobile antennas to get an advantage on the signal. Since a quarter wave is eighteen inches, a gain antenna tends to be longer than a quarter wave and eighteen inches. One has some flexibility in terms of mounting the antenna on a trunk lid, off to one side, and the results are reasonably good.
If you're traveling a lot in between valleys, a quarter wave antenna is preferable. While it has less gain, it transmits higher in elevation. That additional component in the elevated direction can help you hear signals coming from above the valley walls and similarly, helps you to be heard if there is an available path.
In contrast, a quarter wave antenna on 1296 MHz is a little more than two inches. When mounted on the trunk lid, the roof has a substantial effect on the radiation pattern and can obscure contacts. Since the antennas are so small, you can use a gain antenna, such as the Diamond NR-124 which has 8.4 dBi of gain and is only 28 inches long. When mounted on the trunk lid, it offers some visibility above the roof and helps you get out some of the signal.
Still, the roof impedes a good amount of the signal. It's best if you can run a mag mount antenna, and place the antenna in the middle of the roof. You'll enjoy the 8.4 dB of gain in all directions, with no obstruction from nearby features of your car.
Since the wavelengths are 1/8 the size on 1296 MHz, multi-path and mobile picket fencing is less pronounced at normal driving speeds. It has the effect upon picket fencing as if you're driving eight times faster. The received signal would drop in and out faster than the AGC would react, and those brief moments you hear when the signal gets noisy and reemerges from the noise tends to go away. Imaging hearing normally picket fencing at 30 miles per hour, but having it disappear because it seems as if you're driving at 240 miles per hour!
On analog FM, you're more likely to encounter periods when signals can be heard or not heard, rather than hearing the telltale signs of picket fencing that clue you into the fact that you're about to lose a contact. As the gaps in silence increases or the fading noise of bacon sizzling increases, you'll know you're going to lose the signal shortly.
This is more annoying on digital voice using the Icom ID-1 radio, as you really can't tell the signal quality just by listening to the audio. Since it's hard to keep watching the S meter while you're keeping your eyes on the road, you're more likely to briefly hear the other station, then hear silence when the other station becomes out of range.
If you're mobile and the other station is fixed and running a gain antenna, you'll enjoy the greater opportunities at simplex operation. If there's buildings or other large structures that the fixed station can use to bounce the signal, it tends to give the effect as if he's operating a repeater on that building. That's especially true if the building is within two to three miles of his location.
The interference free nature of 1296 MHz mobile communications, the high antenna gain possible in small packages, and less picket fencing makes 1296 MHz mobile communications a refreshing change and challenge from two meter simplex operations. Why not be open to give it a try. You'll never see two meter simplex operations in the same way again.
Our next article we will focus on the advantages and fun operating Weak Signal on 1296 and why you really really want to get an antenna up on that tower and have some fun.
Where are the Elmers?
All in all a great way to start the morning, I was shifting over to monitor 144.180 and 144.200 along with 146.520 which is my standard activity setup in the shack and read the news and just listen for a bit, heard a few guys out in East Texas on 146.520, so hoped in and made a contact and then went back to reading the morning news.
And now we move into what my topic of focus is for today.
About 5:14 I noticed, a spike on the display of my Flex at 144.130 MHz, so I dialed up to see who it was. It was two stations, one out of Houston who was struggling to make the station in Louisiana understand what his call sign was. It took them a good 10 minutes to confirm the call and log it, and both were giving each other decent enough signal reports.
After they finally very exasperated ended the QSO, I went back to the Houston Station, who had a KI5 call, so relatively a new HAM. He also happened to hit my HOT BUTTON regarding phonetics. I got on and made contact with him, we had a nice chat for a few minutes, the guy who he just worked was his very first Single Side Band Contact on two meters, and I was his second {So QSL Card will be mailed to him today} turns out he has been licensed for just over 5 months. After I welcomed him to the hobby, and of course welcomed him to Weak Signal and such…I then told him, that he did understand that they entire miscommunication with his call sign was 100% his fault. He was confused and asked me why……He even spelled it out phonetically.
I said that is why, you are using some of the strangest words to spell things out phonetically I have ever heard, and I have heard some really stupid things used over the years.
I told him if he had used standard phonetics that the ear is keyed up and ready to listen for and that when spoken clearly indicate the letter. He was baffled, he had NO Idea that there were a set of standard phonetics out there.
This guy went down a few months back and tested for Technician and General passed both and got on the air and started operating with out any clue what he was doing or how.
Now I will 100% agree that this is how WE LEARN, myself included and we all will make mistakes. But my question to this subject is simply this.
Where are his Elmers?
How do you get tested too general with out a clue.
I’ll focus more on those two questions shortly.
First off, I do not blame this guy at all, he is doing the best he can and I loved his energy and enthusiasm. If he does not discouraged due to the lack of having a quality Elmer guide him, then he will offer a great deal to the hobby. Not many put up a quality SSB Station on VHF this fast into the hobby and he had a fantastic signal.
But this reminded me of a conversation I over heard the other day, I leave the radio’s in the shack on, and I was in my home office working {to pay for said radio’s, as well as food, electricity, etc}. When I heard two local hams, one brand new and the other a seasoned ham.
The brand new ham signal was horrid, very distorted and just sounded like crap. The seasoned HAM working him, noticed he was off frequency and was actually operating 146.525. He directed him down to 146.520 and advised him this was the actually calling frequency, the guy thanked him for that information. He thought the calling frequency was 146.525.
Again this was a brand new HAM so mistakes will be made and that is to be expected. But again he is an EXTRA CLASS Amateur Radio Operator.
Again I ask WHERE ARE HIS ELMERS?
AND AGAIN I ASK: HOW DO YOU GET TESTED TO EXTRA CLASS WITH OUT A CLUE.
Again, I do not fault the operator fully…….He is brand new and trying to learn and operate. But you can make an argument that any band plan clearly shows 146.520 as the simplex calling frequency.
Anyway, this brings me to my point.
#1: We as experienced Radio Amateurs need to start doing a much better job at Elmering the new HAMS.
I think local clubs, upon testing and passing new hams, should then have in place volunteer Elmers they can assign to these new hams to answer any questions, help them out or provide support.
Depending on the interest the new ham has in the hobby, it may not even be members of the club they direct them too.
Far too often I hear a bunch of grumpy old men sit back and make fun of the stupid LID, or bitch about the LID, but they are not doing anything productive to help the new ham.
All of us need to remember that we each started out as new hams at one point or another and by the same token we all made stupid mistakes or lacked knowledge.
We learned one of several ways, we were lucky to pick up an Elmer or we learned from trial and error and making mistakes.
But think how much more rewarding our experiences would have been to avoid some of those really bone headed mistakes.
#2: My other pet peeve, the FCC is always promoting new rule making the ARRL is always promoting one thing or another supposedly to help enhance the hobby.
Something that I think in today’s world of lower tolerance for other peoples to make mistakes and the fact you can study the answers for the test online, memorize them and pass with out any real practical understanding of the test you just passed.
I would really like to see a TIME IN GRADE rule put into place for Advancement.
The entire purpose of the Novice in the old days and the Technician class today is to gain practical experience.
I think a new ham should become an extra, learn the hobby, learn operating practices and gain operating experiences and understand how to properly communicate with each other on the air.
Then say after 6 months or a year of operating be eligible to take the General Exam.
Same thing, build HF operating experience, advance your skills and understanding and then after a year of operating as a General be eligible to take the Extra Class Exam.
I would even support and promote a new Novice level license that came before the Technician and provided limited areas to operate and expired at the end of a year. You either advanced to Technician or you went away.
I am not trying to add a layer of difficulty to gaining new Amateurs, but make the new ham’s experience much more pleasurable and help avoid them getting into trouble in the hobby.
Imagine if someone has no clue what the national 2 meter calling frequency is? Does he have a clue where he can actually even operate on the HF bands or when he is even out of band?
Just some thoughts to think over.
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