New user, seeking setup advice

Captive

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Joined
Oct 12, 2020
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5
Location
Oregon
First post, hello! I've read countless pages and posts on this site, and 10 months into my slow project I think it's time I ask for what things I can do better or what I may have missed. Reassurance would be appreciated too.

History: Started with a single cheap $35 SDR-RTL USB and dipole a year or two ago. I enjoyed it and wanted to install an antenna, get a real scanner, with possibly getting a CB and more.

Goal: Scanning based equipment at first, ~770 MHz (P25) and ~150 (NFM), and expand from there. I had a few CB radios as a teenager, and that was a lot of fun.

I've mounted a discone antenna on the top of the house, grounded the 10ft mast, grounded polyphaser. This past weekend I just ran about 70ft of "USA-Flex 400" coax and am ready to drill a hole in the wall. It's not LMR-400 but it's much better than my existing RG174.
For all external connections, I've gone with the N type connections. For internal, I suspect I'll end up with BNC for most.
This week I'll order a stridsberg multicoupler (MCA208M BNC or N input). I don't know if that comes with a power supply or if I have to sort that out too.

- Other than a multimeter on each section, what equipment can I obtain to check the cable and signal is good along the path?
- What inline component in the office can measure the signal/quality of the signals I am receiving?
- What high quality flexible cable should I use (patch cables) for the last 6 feet between the multicoupler and receivers?
- Do I need to install a second polyphaser immediately before house entry?
- What other equipment/filters/components should I look into?
- I grabbed a bunch of "Snap-on Ferrite" magnets. Do I just clip these near both cable ends, then one or two in the middle?

I'm also seeking recommendations / links on;
- A coaxial switcher. At some point I'll want to buy equipment that can transmit too. Instead of unplugging and reconnecting antenna feed coax from the multicoupler to another patch cable, I'd like a high quality low loss coax switcher.
- Weatherproofing and cosmetic hardware, like an "exterior cable guard" to cover the hole where the feed comes into the house.

My apologies if any of the above seem to be silly questions or unclear. I can post more details if needed.

Thank you in advance!
 

cwhill

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I know the stridsberg MCA208M comes with a power supply. Excellent product and customer support. I also bought their terminators for any open lines I wouldn’t be using. I use the Omni-X and love it. I only listen to 150 MHz and a 850 p25 simulcast. It works well on both systems. I also use a nano VNA to sweep my setups. As a side note everything I know about this hobby I’ve gleaned from the pages in this forum.
 

WA0CBW

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Dec 8, 2011
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Shawnee Kansas (Kansas City)
You only need one polyphaser and it should be mounted near the cable entrance. The polyphaser can also serve as the coax shield ground. All external ground rods need to be connected the main electrical system ground rod(s) per NEC.
BB
 

chief21

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Mar 2, 2004
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If you only have a single scanner, not sure why you're investing in a Stridsnerg multicoupler. If you're thinking of using any type of transmitting radio with the multicoupler - Don't! Multicouplers are for scanners/receivers ONLY. Even an accidental, momentary blip of transmitted RF would likely smoke the multicoupler internals.

I would recommend that you limit your initial efforts to scanning only, otherwise, you might end up purchasing some expensive items that don't properly support your later activities. Do some research, read some books/forums/youtube videos, before you venture into two-way equipment.
 

Captive

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Oct 12, 2020
Messages
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Location
Oregon
Thanks for the replies so far.

The polyphaser is currently inline near the antenna.
A 6 AWG bare copper is clamped to the base of the antenna mast, and runs to the grounding rod in as short/straight line I could get without going back over the roof. The polyphaser is connected to the wire using a small grounding terminal.

Here's the outside setup. The polyphaser is on the end of the visible coax. A longer (60-70ft) coax run now goes from the polyphaser to inside the house. I'll be weatherproofing the connectors on the polyphaser before the wet weather comes.
20210830_175933.jpg

Sorry, I should have clarified - I started with 1 SDR and dipole, and now have many.

No plans to transmit through the multicoupler! Thank you for the reminder.
 

chief21

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Typically, the polyphaser itself would be near ground level (preferably connected directly to the associated ground rod), close to where the coax enters the structure. This allows the grounding path to be as short and as straight as possible. Long runs of ground wire are not effective.
 

Captive

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Oct 12, 2020
Messages
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Location
Oregon
How ineffective will the polyphaser be nearer the antenna end?

The ground rod, and coax entry points are on the other side of the property / building from each other.
 

chief21

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Summer - Western NC; Winter - Tampa Bay FL
A nearby strike is capable of inducing extreme voltages and currents into your antenna and coax. The purpose of any lightning protection device is to shunt dangerous potentials into the ground (and, hopefully, away from the structure and equipment). For the attached ground to be effective, the resistance must be very low in order to "entice" any damaging currents to flow to the ground rather than elsewhere. A long ground wire will not have that effect due to having a much higher resistance.
Since I am NOT an expert, perhaps it might be best for you to research the National Electric Code (NEC) or other documents relating to proper antenna grounding. If I recall correctly, the recommendation is to ground the coax at (or near) the entry point (meaning a ground rod at the entry point) and for that ground to also be bonded to the structure's existing grounding point, usually near the electric meter.
 

mmckenna

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How ineffective will the polyphaser be nearer the antenna end?

The ground rod, and coax entry points are on the other side of the property / building from each other.
Chief is right on. The issue isn't just a direct lightning strike finding your antenna, it's induced energy from a nearby strike. That energy can be induced into the coaxial cable, so putting the lightning suppressor at the antenna is pretty much useless.

The National Electric Code spells this out pretty well. It may be worth the cost to consult with a local electrician on doing this correctly. Getting advice off a hobby website doesn't qualify as 'expert advice'.

You could install a new ground rod directly under your antenna mast. Ground the mast with a straight run of copper wire (6 gauge) right down to the rod.
Have your coax enter the home under the antenna. Put your lightning suppressor there and ground that down to the rod.
National Electric Code -requires- (as in NOT optional) that the new ground rod and the existing home electric panel ground rod be properly bonded together. Failing to do this can result in a voltage differential between the radio equipment grounded to the new rod and the electrical/electronic equipment grounded to the house electrical system.

This can be done pretty easily, but it needs to be done right. Consulting with a pro is a really good idea.
 

Captive

Member
Joined
Oct 12, 2020
Messages
5
Location
Oregon
Existing setup is;
Code:
Mast --(6 gauge bare)-- ground rod.
       |
Coax --Polyphaser
I'll talk to our electrician about a second ground rod near the coax entry point, and bonding it to the existing ground rod. That's going to be a lot of digging, and concrete tear-up.

In the last few days, I made a half-inch hole in the wall, ran the coax into the house and added an N connector on the end.
As a test reference, the NOAA signal went from -37 to -3.

The Nano VNA looks interesting, I was checking that out last year too.

I'm still looking for input on the "Snap-on Ferrite" magnets, sources for great patch cables, and a method to make the house entry hole cleaner (inside and outside). Some caulking and paint will work for now.

All of this input so far is appreciated - thank you!
 

chief21

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I'm still looking for <snip>a method to make the house entry hole cleaner (inside and outside). Some caulking and paint will work for now.
In the past, I have used a short section of PVC and a 45-degree coupling. The short section acts as a conduit through the wall and the 45-degree piece (facing down) acts as a weather port on the exterior. Once the cable is in place, stuff some high-density foam in the PVC to act as a barrier for cold, bugs, etc. Use whatever diameter PVC works best for your situation. If the inside appearance is critical, you can use a plastic, single-hole electrical cover plate to dress the interior.
 

mmckenna

I really ♥ Ø
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Messages
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I'm still looking for input on the "Snap-on Ferrite" magnets, sources for great patch cables, and a method to make the house entry hole cleaner (inside and outside). Some caulking and paint will work for now.
What do you need the ferrites for? The exact usage will dictate the size/mix, etc.

www.theantennafarm.com will do custom made coaxial cable assemblies. You can order whatever you want. Or, if you need a bunch, just order your own connectors, some coax, and the crimpers and roll your own.

As for running cable into the house, you can use PVC electrical conduit and a weather head on the outside. But it really depends on where it's entering. Things like dryer vent covers can be used, PVC fittings, or install a PVC junction box on the outside with a PVC feedthrough into the home.
 
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