Routing cable

[Santacarl]

Hello all,

I'm new to this world of radio. I am starting with a scanner with the goal of getting to a HAM license and since I live out in the 'boonies' I'm thinking there's a possibility that I'll need an outdoor antenna to pick up some areas of interest. I don't have the scanner yet so I haven't tested reception with just the indoor antenna yet. I'm just thinking ahead.

I am looking at the Unidens....the BCDx36HP line which covers a pretty wide frequency range. So when it comes to cable I'm wondering the best way to go.

I should caveat that with this factor.....the 'spousal unit' factor! I need to move the antenna away from the old homestead to where it's less apparent. So, I'm looking at a run of around 150 feet.

I understand that most signal loss occurs when you transmit and reception is somewhat less problematic but here's the rub. In order to place the antenna at 'that' location I would have to go underground..... So here are a few issues I'm confused over and would appreciate any feedback to help spin me up to speed.

At that distance (150') and the frequencies covered by the scanner (assuming I can go under ground) which cable is best suited?

Since the goal is HAM later on it wouldn't hurt if I could find a coax that I could use for that also.....just in case...

If I can go underground...does that require conduit or do you just bury the coax in the ground?

Thanks...

SC

 

[gewecke]

I suggest dramatically decreasing that feedline length by using antenna configurations which you might be able to "disguise" as something else or maybe blend in so its more spouse friendly? Less feedline will improve reception tremendously too. 73, n9zas

 

[Santacarl]

I suggest dramatically decreasing that feedline length by using antenna configurations which you might be able to "disguise" as something else or maybe blend in so its more spouse friendly? Less feedline will improve reception tremendously too. 73, n9zas

Thanks Gewecke....

I was afraid that might be the case....being new to the 'sport' I thought I'd at least ask to see what I'm dealing with.... The "disguised" configurations is a problem as there is little to no place to hide them...about the tallest thing in my yard is a fence post and that's down in the low spot in the yard.....Ha...

 

[gewecke]

Last but not least, trying explaining to your spouse that this is your new passion, er um hobby? She could look at the bright side ... you would be home more? ::lol::roll: 73, n9zas

 

[Blackswan73]

How about a new "flagpole" to show your patriotism?

 

[Voyager]

Yea - 150' is at the point you will need feedline that will run around $750 to get any reasonable loss, and that will still be about 50% loss at UHF. Not sure if the spousal factor is involved there or not, but is spending $750 really "better" than a visible antenna?

I would use a vertical disguised as (or in) a vent pipe, and run a much shorter feedline.

Using typical scanner 50' feedline, you would lose about 90% of the signal in your 150 foot feedline, but only about half in the 50' feedline. If you can make it shorter, all the better.

To paraphrase an oldie but a goody: "My wife said it was her or the antennas. I miss her."

 

[Santacarl]

How about a new "flagpole" to show your patriotism?

Already have a flag pole and it's about 100' away and on the other side of the drive way....It's anchored in about 2' of concrete!

Thanks for the thought though....

 

[Santacarl]

Yea - 150' is at the point you will need feedline that will run around $750 to get any reasonable loss, and that will still be about 50% loss at UHF. Not sure if the spousal factor is involved there or not, but is spending $750 really "better" than a visible antenna?

I would use a vertical disguised as (or in) a vent pipe, and run a much shorter feedline.

Using typical scanner 50' feedline, you would lose about 90% of the signal in your 150 foot feedline, but only about half in the 50' feedline. If you can make it shorter, all the better.

To paraphrase an oldie but a goody: "My wife said it was her or the antennas. I miss her."

Shorter is better? Okay now I AM confused..... I thought the idea was to get it up above surrounding structure/trees etc?

You mentioned a "vertical" would you have a model number that I could reference to make sure I understand what we're talking about? I was thinking I might need a Discone Antenna...or is that not the proper type for a scanner?

"Her or the antennas".....That's a good one....

Thanks for the response.....

 

[N5TWB]

Shorter is better? Okay now I AM confused..... I thought the idea was to get it up above surrounding structure/trees etc?

You mentioned a "vertical" would you have a model number that I could reference to make sure I understand what we're talking about? I was thinking I might need a Discone Antenna...or is that not the proper type for a scanner?

"Her or the antennas".....That's a good one....

Thanks for the response.....

First, here's the vent-mounted antenna referred to: Ventenna

A discone is a specialized vertical antenna and it can be used for a scanner. Its benefit is that it is very broad-banded and that is also its drawback. You say you are out "in the boonies" so it's possible you may require some gain from your antenna and a discone does not provide gain in the signal. Please read my post in your other thread about experimentation. You need data in order to better understand your situation and any possible solutions.

Based on the info in your other thread and here, a discone could work for your frequencies of interest but is probably not going to get good marks on the spouse approval scale. As others have already noted, your thoughts on getting points on the spouse approval scale by going far from the house will quickly exceed standard cost/benefit ratios. Again, go read my other post on experimentation.

 

[gewecke]

Shorter is better? Okay now I AM confused..... I thought the idea was to get it up above surrounding structure/trees etc?

You mentioned a "vertical" would you have a model number that I could reference to make sure I understand what we're talking about? I was thinking I might need a Discone Antenna...or is that not the proper type for a scanner?

"Her or the antennas".....That's a good one....

Thanks for the response.....

when we say shorter feedline, we mean less distance from radio to antenna meaning the majority of your coaxial cable should be focused on getting your antenna as high as possible to increase your line of sight. You mentioned a antenna for your scanner which eventually could be used for ham radio if you decide to license? Google the Diamond X50A to start with its small, only 5'6" tall and is designed for the 2meter/70cm bands (vhf/uhf) so it would be suitable for your scanner too. Also a Discone antenna comes in many sizes and will work for either a scanner or amateur radio, and as mentioned there's the "Ventenna" but is somewhat limited for amateur radio. 73, n9zas

 

[FKimble]

Sounds like you need to put the antenna in the attic. If you don't have a metal roof, then you can mount the antenna so it almost touches the peak of the roof. Keep it away from metal duct work, heating/AC units and wiring.This will get your antenna up fairly high, and the much shorter coax will give you a much stronger signal than the 150 feet of coax location. Mount the antenna to use the minimum amount of coax. And "loss" in coax is equal in both direction, transmit and receive. An don't scrimp on coax or antenna. You need a good antenna to catch the most signal and good coax to to take that signal to the radio. And I second the Diamond X50 antenna.

 

[popnokick]

Don't combine your scanner antenna with your amateur radio antenna(s). As explained in your other thread in this RR forum, your best option is to use your old TV antenna in the attic for your scanner! Read more here:
http://forums.radioreference.com/scanner-receiver-antennas/328310-dont-laugh-please.html

 

[gewecke]

Don't combine your scanner antenna with your amateur radio antenna(s). As explained in your other thread in this RR forum, your best option is to use your old TV antenna in the attic for your scanner! Read more here:
http://forums.radioreference.com/scanner-receiver-antennas/328310-dont-laugh-please.html

I don't think he means combine so much as using it for dual purpose, which makes sense to start with. 73, n9zas

 

[jeatock]

It is not difficult.

Yep, you can put an antenna many hundreds of feet away from the receiver. I design and build such systems all the time for public safety and business applications. All it takes is dollars.

Simple reality: transmitting antennas need to resonate end to end lest the little electrons bounce back into the transmitter and let the magic smoke out. An antenna system that transmits properly at extreme low power will rock receiving the same frequency neighborhood (with limitations).

Another reality: an antenna system like the above will receive well across the entire band it is tuned for, and will work out of band with some loss only because the antenna is not resonating as efficiently on out-of-band frequencies. In many single-frequency applications I have to install notch filters to keep other frequencies out. Receiving is much more forgiving and/or quirky than transmitting, and something not technically supposed to work may actually work quite well.

I have always found that radio is one quarter science, one quarter black arts, and one half dumb luck.


Adding any connections and coax introduces an attenuation loss. Check the attenuation per foot of any interesting coax and the connector specs to see what the losses are. (LDF coax and N-family connectors are best.)

Now do some simple math. A 3db per 100' coax loss means that only half of the signal going in on the far end comes out 100' away at the radio. (Each 3db loss or gain is a factor of 2.) At 200' the loss for the same type of coax is 6db, half-of-half or 3/4's lost. 300' of bigger/better 1db loss coax has the same attenuation as 100' of the 3db loss coax.

At 100' if the receiving antenna has a 6db gain (in the targeted frequency range) the math is (-3db coax loss) + (6db antenna gain) = (+3db overall gain). At 200' (-6db coax loss) + (6db antenna gain) = (zero overall gain/loss). It is not complicated.

The same works on transmitting: if you push 100 watts into a 3db loss coax, you only get 50 at the antenna. A 6db antenna (factor of 4) gives you an ERP of almost 200 watts (50x4=200). ERP is what really counts. Need 300 watts ERP? Crank the horsepower up to 150 and damn the losses.

(And yes, I know that there are many other factors that come into play. But this is Antenna 101, okay?)

Practical reality: a telescoping antenna on the back of the radio pulled to a 1/4 wavelength has an attenuation of about zilch on that frequency range. 1/2 wavelength has about 2db of gain, and 5/8 wave is about 3db. (More than 3db gain requires phased element antennas.) If your house walls create 3db loss, a 3db coax loss to an antenna will only get you more signal vs. the telescoping antenna if the remote antenna has more gain and is mounted substantially higher.

Always remember that while there are many common theories and components, receiving and transmitting are always entirely different paths. Doing both on the same antenna system is not always possible when different frequencies are needed.


A wide-band amplifier at the antenna will push the signal to the receiver. That is how CATV cable TV systems work. The receivers at the head end feed into wide-band amps that push MTV and FOX into the coax system. Booster amps downstream keep pushing until it gets to your house. Most CATV systems need to install attenuators on the pole to keep from smoking your TV.

If you have a 6db coax loss, a 6db wide-band amplifier at the antenna will zero out the coax attenuation, and more amplifier gain means more signal (and noise unless it is filtered properly). Feed the pre-amp with a gain antenna and the amp will have more signal to work with. Just don't try and transmit through it. A wide-band amplifier at the receiver end won't work as well since it is sucking static and noise along with any desired signal.

To the detriment of folks making a fortune from 'special' antennas and coax, an improvement of less than 1.5db isn't worth any real money. I often switch between a 1/4 wave zero-gain and 3db gain antenna on my truck. Same location and mounting, same radio, but different antenna. While the 3db gives me twice as much transmit power, there is very little difference in receive performance.

Also, plain old CATV pre-amps work surprisingly well in scanner applications. Buy a couple "F" to "BNC" adapters and you're in (you can totally ignore the 75-ohm to 50-ohm impedance mis-match).

Water is NOT your friend, has nothing but time on its side and is tirelessly trying to get into your installation and steal signal. Moisture will seep right through common coax, and you cannot waterproof connectors too much.

Lightning is not good either, but that topic is covered in dozens of other posts.

 

[popnokick]

Also, plain old CATV pre-amps work surprisingly well in scanner applications. Buy a couple "F" to "BNC" adapters and you're in (you can totally ignore the 75-ohm to 50-ohm impedance mis-match).

+1 on that.... my experience exactly. And also another reason not to plan on "dual purpose" use (Rx and Tx) for the antenna. While 75 ohms is fine for the scanning receiver, your ham transmitter is not going to be happy or simple to deal with into a 75 ohm cable that also has a receive preamp. And if you transmit into the receive preamp, it will probably let out a little "I give up" squeak.... and never work again.

 

[Santacarl]

First, here's the vent-mounted antenna referred to: Ventenna

A discone is a specialized vertical antenna and it can be used for a scanner. Its benefit is that it is very broad-banded and that is also its drawback. You say you are out "in the boonies" so it's possible you may require some gain from your antenna and a discone does not provide gain in the signal. Please read my post in your other thread about experimentation. You need data in order to better understand your situation and any possible solutions.

Based on the info in your other thread and here, a discone could work for your frequencies of interest but is probably not going to get good marks on the spouse approval scale. As others have already noted, your thoughts on getting points on the spouse approval scale by going far from the house will quickly exceed standard cost/benefit ratios. Again, go read my other post on experimentation.

Ahhhh, the gain monster....didn't realize that drawback on the discone....

I didn't realize that cost factor either as it relates to upgrading type of coax due to length....As mentioned the cost/benefit ratio is not there.....

I'm all for the experimentation idea too....but I'm so new to this that I don't even know where to begin the trial and error in some cases. Coming here and asking questions is helping focus me into the areas I need to harvest the data from.

Thanks for helping me in that regard and explaining so that I understand some of the attributes of 'verticals' better....I'm learning and those of you who are kind enough to coach us newbies are very much appreciated....