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Antenna Issues
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lanceboil
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Joined: 10 Aug 2002
Posts: 13

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Hello,
I went to a local radio shop that specializes in industrial transmitters and two-way radios. I had them construct for me a 50 foot length of RG-58 cable with a PL259 on one end, and a BNC on the other so it would connect to my Comet CFM 95SL 5.8th wave antenna. My point being to illustrate that I have a good quality cable and antenna.

Now my antenna is mounted to the TV antenna mast on top of my house. I built a stand-off that holds the antenna out away from the mast a bit, about 10 inches or so. This mans that the main upright of the antenna is paralell to the TV antenna mast, and is 10 inches away from it.
It is not touching the mast or guy wires in anyway (except the stand-off which is insulated)
My TXR (Max-1) supposedly kicks out 5 watts. However, I cannot pick up my signal over four blocks away. I think this is odd, and probably means that something is not working correctly.

What should I be looking for? What possible problems could I have? I do not own an SWR meter or freuency counter, so I cant do any of that kind of diagnostics.
Also, from time to time my PLL light will blink on and off, as though it is going in and out of PLL. What would cause this?

And grounding: Should my antenna be grounded? And grounded to what? And how? There IS a ground on the TV antenna mast, but my antenna is not electrically connected to that.

Could my antenna being that close to the mast be causing interference or screwing up my signal strength?

My antenna cable is dangling against the side of myhouse, and runs along the roof, laying directly on the shingles, would this cause interference? Would it cause signal loss? Should I get some little stand-off screw-in holder thingies to hold the cable away from the house and shingles?

Your valued input would be most appreciated!

Cheers,
lanceboil

Wed Aug 14, 2002 5:31 am View user's profile Send private message Yahoo Messenger MSN Messenger
StormiNorm
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First of all Sir. Lancelot(trust you take no offence in my dubbing you with such esteeemed annointment)

I must commend you for your depth of explanation and detailed pin pointed references etc.etc.I think this is most commendable and a definite trend that should be encouraged by all to adopt.In my views such clarity and attention to detail goes a long way in solicting help,and thereby others can learn from you equally as anyone else on this forum...And i am gonna break away from a decision i just made to the fact that i think it would be in the best interest of all that i remain silent,unless my views are explicitly requested...Now that would not be too humble an action to adopt...i am not one to be silent,so consequently i would imagine that my departure has arrived...I can detect the fact that some folks are getting a bit bent out of shape...I am the type of person that has a burning desire to share my knowledge and experience.I fully realize that i am NOT THE OWNER OF THIS FORUM,and further more all that i can foresee is my continual contribution,and in no doubt it is just a matter of time before Topics addressed by me will supercede anyone else.....So sadly tis time to go.How ever before that happens please allow me to share a few real world suggestions regarding your problem.

a)A VSWR meter is a absolute must,whether or not you are technically challenged,however i see that you have taken steps to secure some help...very good!!!

b)may i suggest that it would have been a better choice in useing RG8 OR RG213 as the feed to your antenna..At 5watts you need to minimize your feed cable losses.you need to get as much of that 5watts up to the antenna to be radiated as a usefull signal.

b)It may have been a good idea to have them at the Local Comms. Shop tune your antenna to your desired frequency...Once tuned you can easily transport the comet with the Radials removed,and easily re-attached back home,without any critical loss of tuning resonance.

c)Even although the PL259'S were not fitted by you,It might be a good idea if you were to remove the cable at least and have them check it for dc continuity and shorted conductors..I would assume that if they were professional enough,that was done...but we all can make a mistake..even the pro's.

d)Also if you decide to pay another visit to the shop,then take the TX. and have them Bench and feed it into a dummy load/wattmeter to verify the oput power.

e)The mounting configuration bothers me a bit...It would be advisable to mount the comet above the TV antenna if possible...also you may find that you may, have a fair amount of RF feed back into your tv,due to the close proxmity of both Antennas,even at 5watts...If you are useing a outside Antenna that would indicate to me that you are in a fringe area as far as tv reception is concerned.

f)Yes it is a very good idea to ground the mast that the Comet is supported by..Just run a mininium length of regular electrical wire over to point where the tv antenna is grounded,and make sure that the eventual run is attached to a earth ground at the bottom.

g)Also may i suggest that whatever cable that you use as a feed,Right at the mounting collar of the commet,make a 5turn coil,of about 5inches in diameter(useing the coax)and tie-wrap or tape the turns together....Also try to secure the cable at a few points on the mast,to prevent it from "slapping" around.

Trust that my suggestions may be of help to you...also if you are still in doubt as far as the audio bit is concerned,please feel free to drop me a line if you need further assitance.i would rather prefer to refrain from posting some archived notes..My pleasure

Keep up the good work...You are definitely on the right track Sir.
Wed Aug 14, 2002 10:15 am
lanceboil
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Joined: 10 Aug 2002
Posts: 13

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Quote:

n 2002-08-14 05:15, StormiNorm wrote:
First of all Sir. Lancelot(trust you take no offence in my dubbing you with such esteeemed annointment)[/i

Hmmm...Maybe if I used the right annointment, then I wouldnt have to Lance the Boils?

[i]ust commend you for your depth of explanation and detailed pin pointed references etc.etc.I think this is most commendable and a definite trend that should be encouraged by all to adopt.In my views such clarity and attention to detail goes a long way in solicting help,and thereby others can learn from you equally as anyone else on this forum.


Thanks, I try....I dont expect any answers or solutions that are any more detailed then the questions asked.
I am also not ashamed to ask those seemingly silly, stupid, simple questions....it seems to be a human factor that wen we start thinking we know everything that we start tripping over the really basic simple stuff...this is the univrses way of lampooning us.

a)A VSWR meter is a absolute must,whether or not you are technically challenged,however i see that you have taken steps to secure some help...very good!!!

Yesterday I made a trip out to the local State Surplus Property warehouse. The last time I was out there, they had MOUNDS of electrical and radio equiptment, including SWR meters, Freq counters, multimeters, lab power supplies, osciliscopes, etc etc etc...This gear came out of various State depts, and Vo-Tech schools.
And I am now kicking myself quite throuroughly for passing up on buying some of this stuff!
I point this out for everyones benifit: Check around your area for State (or federal) surplus property auctions or warehouses that sell to the public...you can find some wild stuff.
Our state currently has FOUR commercial-grade antenna towers for sale: Like big ole 100 foot or so jobs, two are on the ground, two must be taken down and hauled off.

These things can be a good source of stuff for people....They also have a huge pile of old Motorola two-way radio (high band FM) repeaters and TX/RXers.

b)may i suggest that it would have been a better choice in useing RG8 OR RG213 as the feed to your antenna..At 5watts you need to minimize your feed cable losses.you need to get as much of that 5watts up to the antenna to be radiated as a usefull signal.

I thought about that...itwas a financial decision to go with the RG58 instead of RG8. The RG8 was about $1.10 a foot compared to $.68 cents a foot for the RG58.

b)It may have been a good idea to have them at the Local Comms. Shop tune your antenna to your desired frequency...Once tuned you can easily transport the comet with the Radials removed,and easily re-attached back home,without any critical loss of tuning resonance.


The Comet is tuned by sliding the top element up and down. I did this using the chart. But I have no way of actually double-checking it.

c)Even although the PL259'S were not fitted by you,It might be a good idea if you were to remove the cable at least and have them check it for dc continuity and shorted conductors..I would assume that if they were professional enough,that was done...but we all can make a mistake..even the pro's.


I could check for continuity, thats no big problem. I really do not think that is the problem though...but it IS good advice...one of those simple things that we easily overlook.

d)Also if you decide to pay another visit to the shop,then take the TX. and have them Bench and feed it into a dummy load/wattmeter to verify the oput power.


I might just have to do that....it seems that I have developed another problem with this thing as well....I now get no LCD comming on when I power it up, and I cannot determine any event that might have affected the LCD...it just stopped working. The transmitter itself still works, but sounds "crappy". Ive checked wires and connections, but cannot see anything obviously shorted, and this looks like a different LCD then was used in other Max 1 units.

e)The mounting configuration bothers me a bit...It would be advisable to mount the comet above the TV antenna if possible...also you may find that you may, have a fair amount of RF feed back into your tv,due to the close proxmity of both Antennas,even at 5watts...If you are useing a outside Antenna that would indicate to me that you are in a fringe area as far as tv reception is concerned.


The TV antenna is a hold-over from those days...and was left on the roof in case the previous occupants decided they didnt like cable...I thought it made a suitible mast to mount my antenna to. There are two other TV reception antennas on the mast. It would be very difficut to mount the Comet above the other antennas. But perhaps I should just get a different roof-mount and mount the comet elsewhere on the roof?

In otherwords, I am not concerned about getting RF interferance into the TV antennas: They arnt being used for anything but bird-roosts.
I am concerned if the close proximity might create rf interferance to my Comets output.

f)Yes it is a very good idea to ground the mast that the Comet is supported by..Just run a mininium length of regular electrical wire over to point where the tv antenna is grounded,and make sure that the eventual run is attached to a earth ground at the bottom.


OK, just to be a bit more specific...are we talking about grounding the MAST only, or grounding the antenna itself? or both? As it is now, the antenna is completely insulated from anything except the cable. The TV antenna MAST is grounded. I built my stand-off apperatus out of PCV pipe and wood, there is no electrical connection between my antenna and the mast.

How do I ground the 'eventual run' of the cable?

g)Also may i suggest that whatever cable that you use as a feed,Right at the mounting collar of the commet,make a 5turn coil,of about 5inches in diameter(useing the coax)and tie-wrap or tape the turns together....Also try to secure the cable at a few points on the mast,to prevent it from "slapping" around.


I will give that a try as well....Does it matter that the cable is just laying on the roof?

Trust that my suggestions may be of help to you...also if you are still in doubt as far as the audio bit is concerned,please feel free to drop me a line if you need further assitance.i would rather prefer to refrain from posting some archived notes..My pleasure

Keep up the good work...You are definitely on the right track Sir.


Well thank YOU for your kind and much appreciatedimparture of knowledge!
I have built a few Ramsey kits in the past, and am a Sound Engineer by trade...but that certainly doesnt mean that I know anything about RF circuits, opperations or even electricity.

Cheers!
lanceboil
Wed Aug 14, 2002 5:53 pm View user's profile Send private message Yahoo Messenger MSN Messenger
StormiNorm
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You may want to verify that there is a dimmer control pot i think i am not sure,for the max1.I have not come into contact with too many,usually in and out the door..the M1P has a display brilliance control..maybe Marko may elaborate,but i gather that you have received a copy of the manual,hence follow the instructions.

Also if you are are useing an insulated support,then attach the ground lead right at the mounting collar at the base of the "Halley's" Comet

Wed Aug 14, 2002 8:07 pm
StormiNorm
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Also may i add that surplus outlets are indeed a good place to obtain various sundry items that a D.I.Y LPFM activst can utilize.

Be very cautious about the idea of being able to utilize commercial unit to LPFM usage..No replies please i shall expound on that at some point in time..somewhere....This topic is closed as far as i am concerned...DONE DEAL!

StormiNorm
Thu Sep 05, 2002 7:08 pm
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