?? on Alpha-Delta DX-SWL Sloper

[datainmotion]

Two questions:

1. The upper attach point is approximately 28ft AGL and the lower is attached to the shed roof at approximately 9 ft AGL. Would I be better to anchor the lower end at ground level rather than 9 ft off the ground?
2. The upper attach point is at the NE while the lower is at the SW. Should I expect the best RX to be to the NW and SE with this arrangement?

Thanks,

Mike

 

[SCPD]

Answers:

#2 - Yes but the directivity of a wire is pretty insignificant. In most cases, you can make it directional by adding a 600 ohm 1/2 watt resistor to the lower element (and then grounding that side to earth ground.) This will get you reception in the direction of the antenna.

#1 - Remember that the "zone" of EMI is about 10m from the house. Ideally, you'd want say a 10ft (or higher) pole on top of a roof (to get around the interference zone.) Also, if it's a metal shed, this could affect your receiving sensitivity. It's not usually significant, but it depends on its construction, etc. If it's a plastic shed (aka tuff shed) then it shouldn't be a problem. To answer your question, you ideally want to make a 35-45 deg angle. The higher off the ground the better. Also, be sure to ground the antenna to rid yourself of static build-up. I've personally never witnessed a grounded antenna making things "worse" than an un-grounded antenna - so imho, it's something you do by default.

Also , be sure to use quality coax leading into the house. Do not use RG-58 you buy from Radio Shack. You need at minimum RG-8 or RG-213. LMR400 or LMR600 is the best.

 

[datainmotion]

Answers:

#2 - Yes but the directivity of a wire is pretty insignificant. In most cases, you can make it directional by adding a 600 ohm 1/2 watt resistor to the lower element (and then grounding that side to earth ground.) This will get you reception in the direction of the antenna.

This is good as I want it to as "omni-directional" as possible.

#1 - Remember that the "zone" of EMI is about 10m from the house. Ideally, you'd want say a 10ft (or higher) pole on top of a roof (to get around the interference zone.) Also, if it's a metal shed, this could affect your receiving sensitivity. It's not usually significant, but it depends on its construction, etc. If it's a plastic shed (aka tuff shed) then it shouldn't be a problem. To answer your question, you ideally want to make a 35-45 deg angle. The higher off the ground the better. Also, be sure to ground the antenna to rid yourself of static build-up. I've personally never witnessed a grounded antenna making things "worse" than an un-grounded antenna - so imho, it's something you do by default.

I have the upper end fastened to the metal flashing on the chimney, so it looks like I should move that off to a non-conductive surface (PVC possibly?). Also, on the lower end, the shed is wood. I would say my angle is probably between 40 and 45 degrees (w/o doing the math). On the grounding, what are you saying should be grounded?

Also , be sure to use quality coax leading into the house. Do not use RG-58 you buy from Radio Shack. You need at minimum RG-8 or RG-213. LMR400 or LMR600 is the best.

I am using Times RG-8X cable currently.

 

[SCPD]

Yeah you might consider a 10ft piece of PVC pipe attached to the chimey flashing to raise the height a bit and get it away from that flashing. As long as the end isn't attached "directly" to the flashing you should be okay.

More importantly, you should dump that RG8x coax. You can buy RG8 (the thick stuff) at Radio Shack (some times... it's getting hard to find there now.) If your coax is just going into the house directly (i.e. a short run) then you might look into LMR600. It's not too bad (price wise) in shorter runs.

A short run of RG8x isn't going to penalize you that much but the thicker RG8 or LMR will help rid yourself of local EMI sources from inside the house.

What radio are you hooking this up to? If the radio is a portable-type then I wouldn't worry too much as the radio probably isn't sensitive enough to know the difference. If it's a R75 or newer desktop then by all means you want to rid yourself of as much noise as possible.

As for grounding, if you look at Universal Radio's web site on this antenna, they show the 'downlead' as being able to be grounded. You should try it without a ground and with a ground. I bet you'll get better signal strength with it grounded.

 

[datainmotion]

Yeah you might consider a 10ft piece of PVC pipe attached to the chimey flashing to raise the height a bit and get it away from that flashing. As long as the end isn't attached "directly" to the flashing you should be okay.

Will do - once the snow melts off the roof

More importantly, you should dump that RG8x coax. You can buy RG8 (the thick stuff) at Radio Shack (some times... it's getting hard to find there now.) If your coax is just going into the house directly (i.e. a short run) then you might look into LMR600. It's not too bad (price wise) in shorter runs.

A short run of RG8x isn't going to penalize you that much but the thicker RG8 or LMR will help rid yourself of local EMI sources from inside the house.

The run is about 50ft. And just to clarify, it is TerraWave's version of LMR-240. Should I still change it to RG-8? I do have enough CommScope RG-58/U to replace it with as well...

What radio are you hooking this up to? If the radio is a portable-type then I wouldn't worry too much as the radio probably isn't sensitive enough to know the difference. If it's a R75 or newer desktop then by all means you want to rid yourself of as much noise as possible.

An SDR-IQ.

As for grounding, if you look at Universal Radio's web site on this antenna, they show the 'downlead' as being able to be grounded. You should try it without a ground and with a ground. I bet you'll get better signal strength with it grounded.

I have heard this both ways. I am willing to ground it though as it doesn't appear it will hurt anything - worst case being no change.

Thanks for your help!

 

[SCPD]

Yeah, so it's a set up you'll want to do right.

Here's the basic breakdown for coax:

TYPE @10mhz @30mhz

RG-58 -1.5db -2.6db
RG-8 -0.5db -0.8db
RG-8x -1.0db -2.0db

LMR240 -0.8db -1.3db
LMR400 -0.4db -0.7db
LMR600 -0.2db -0.4db

The loss is at 100ft lengths. The LMR240 is fine for now. In the future, you could run a 50ft length of LMR400 or LMR600. You may or may not have problems with inside interference.

For the SDR, you'll need a BNC cable. You may want to buy an antenna switch, and that way you can have a plug-in for a radio and then a short piece of LMR100 coax to the BNC port of the SDR.

Here's the item I'm talking about:

http://universal-radio.com/catalog/cable/4791.jpg

No problem on the help. Let us know how the SDR works out!