Noob question on Antenna (again..)

[alokpant]

Hi, I recently started fiddling with SDR radio and am still learning the ropes. I dont have much background on radios, cables, Antenna and making baby steps. I am using SDRPlay SDR and currently using indoor antenna. I recently purchased a discone antenna (Tram 1411) and its in my study room with lot of interference. It seems to work OK but I think it does pick up lot of noise due to all the other electronics inside the house. The antenna connector is USF female and SDR connecter is SMA/BNC I have some very basic questions if you can help

Moving the antenna to attic: I have internet cable connection from attic to my study. I think its a coax cable with RG59 connectors. I hear there are different impedance and loss of signal due to mismatch. So the question is
a) It seems I need to additional two cables (Attic: USF Female to RG59) and another (Study: RG59 to SMA/BNC). Will this cause lot o attenuation. What is the best route here?
b) I don't want to spend lot of money building such cables. What is the economical options. Where can I get prebuild cable (~15 feet)
c) Dump question- Do I need grounding arrangement etc with this antenna?

Moving the Antenna to outside:
a) I have a window in my study. Is there good way to bring Antenna cable from outside to indoor (~50-75 feet wire without drilling the walls etc) I saw some pictures of thin cable that can be be brought in via window. Is there such an option

Listing to AM radio
I am very interested to listen low HF AM (0-30MHz) radio specially cross country. I tried spreading a simple long wire and using this as antenna but the reception is poor. I hear about loop antenna etc. Is there one such prebuild antenna that I can purchase. Again what is the best place (attic/Outdoor)

Any suggestions pointers on all the three aspects will be greatly appreciated

Thankyou

 

[devicelab]

Yes, you need to get your discone antenna outside. You'll have nothing but issues if it's indoors. It can even be put on a deck if necessary. Ideally it needs to be up high -- as high as possible. Obviously, you'll need a longer run of coax if you do this...

For now, stick with RG-8X coax. It's cheap but very effective. It's not ideal but for the time being it's fine. You can order this from Amazon. You can order it with various connectors or you can get PL-259 connectors on the coax and just buy an adapter for your SDR.

Example: https://www.amazon.com/Cable-Experts-RG-8X-Coax-Weatherproof/dp/B07V5WRP6S

Random wire antennas for HF are OK but in high-noise environments they don't work well. Loop antennas are better and they're amplified so it can help to bring your HF signals better.

A popular loop is this model: https://www.w6lvp.com/product/amplified-receive-only-mag-loop-antenna-with-power-inserter/

ANTENNAS ALWAYS GO OUTSIDE...

There are ways to bring coax inside a house but sometimes you'll have to get creative.

Here's the ribbon feed -- which I've never used -- so I can't comment on how well it works: Diamond MGC50 Feed Through

If you have windows that slide down from the top, then MFJ makes a 'window passthru' box which allows the window to close and the box has connectors on it. MFJ-4601

Here's the MFJ model in action:

 

[alokpant]

@devicelab Thankyou very much for prompt reply. You have been very helpful. Thankyou!

MFJ4601 seems a good option for me and I just ordered it. I seek some more advise on this
1. In my case cable length need to be ~75-100 feet to run from my office window to back and top. Will RG8X be reasonable OK for that length. The link you shared have 100 feet option with PL259 and works well in my case
2. The picture you shared is very helpful. Can you explain this arrangement. It seems there are two wires that are connected from the board and finally to one single cable going to Antenna perhaps
3. If I connect two antenna outdoor, Do I need two 100 feet long cable or somehow there are be splitter arrangement to bring both Antenna signals via single cable. Based on your picture seems I can get by single cable somehow (not sure how..)
4. Where can I get info on how to ground these Antenna connection (or just grounding this MFJ4601 is good enough)

Thankyou again

 

[devicelab]

1. In my case cable length need to be ~75-100 feet to run from my office window to back and top. Will RG8X be reasonable OK for that length. The link you shared have 100 feet option with PL259 and works well in my case.

It's not the ideal coax. The ideal coax is LMR400 but it's very stiff and much more expensive. RG8x is not the worst but not the best either. LMR400 @ 100ft can run you anywhere from $125 to $250 depending on brand, who makes it, connectors, etc. The RG8x will give you less performance the higher in frequency but the cost savings might be significant.

2. The picture you shared is very helpful. Can you explain this arrangement. It seems there are two wires that are connected from the board and finally to one single cable...

Negative. This is two coax feeds (from two antennas) being grounded directly to a ground rod via lightning arrestors. Lightning arrestors need to be grounded directly to work properly. Then there are two cables going to the MFJ-4601. So (2) specific antennas.

EDIT: I just noticed in that picture -- the owner has one antenna disconnected. There are (2) connections there though.

If you can get the discone up high AND you live in high-lightning area then you may want to consider a similar configuration.

3. If I connect two antenna outdoor, Do I need two 100 feet long cable or somehow there are be splitter arrangement to bring both Antenna signals via single cable. Based on your picture seems I can get by single cable somehow...

Negative, you'd want to use an antenna switch. Generally I'd only recommend switching antennas of similar frequencies. So if you're thinking HF and DISCONE -- then keep those on separate coax connections. Don't switch them.

The nice feature about the MFJ-4601 is that on the "inside" of the box, you can use short RG-8x coax at whatever length you require. You can get one end with PL-259 and the other with BNC (or SMA) -- whichever you need. The short jumper will not make a difference to your signals.

4. Where can I get info on how to ground these Antenna connection (or just grounding this MFJ4601 is good enough)

Yes, in most cases, you can install an 8ft ground rod into the soil (near the MFJ-4601) and connect the MFJ to the ground rod directly. If you live in a high lightning area then you may need to consider an arrestor.

Here's a book for you: https://www.amazon.com/Grounding-Bonding-Radio-Amateur-ARRL/dp/1625950659

 

[alokpant]

Thankyou devicelab

Yes LMR400 is expensive for someone who is just experimenting. May I ask what be be better option among the three possible option for me

a) Discone antenna inside at my study (short cable but surrounded by several interference)
b) Disone antenna at Attic while utilizing existing RG6 internet cable that runs from my attic to office (~25 feet long). I think this has 75 ohm impedance and I need to add two additional converter on each side (SMA, UHF)
c) Outside Antenna at back of my house (elevated) with RG8 (~100 meter run)

Thanks
-Alok

 

[devicelab]

May I ask what be be better option among the three possible option for me

c) Outside Antenna at back of my house (elevated) with RG8 (~100 meter run)

IMHO, there's no option. I know people have antennas in attics/indoors but I think it's pretty pointless. It comes down to what you're trying to hear ultimately. An outdoor antenna is like having really bad eyesight and then wearing corrective glasses for the first time.

Also just FYI, there is RG8 and RG8x -- they are two different types just to be clear. You want RG8x.

 

[alokpant]

Thankyou. I have ordered RG8x with 100 feet. Hopefully will get all this in few days and I will update with my results and hoping it will be like the corrective glass as you said even if the length is not optimal..

 

[devicelab]

Sure let us know how it's going.

 

[alokpant]

@devicelab, Just go the cables. Yes even with 100 meter cable and discone antenna standing at my outdoor covered deck floor outside, the quality seems much better (snap shot attached even at low HF freq with discone antenna)

Thanks for your advice.

BTW back on discone Antenna, are there more economical option on loop Antenna etc. $250+ seems a good investment that I can use for other items. Any sub $100 option

 

[devicelab]

Yes, there's a new loop that has grown in popularity recently. I have NOT used it so I cannot give you any feedback. While it isn't perfect, it is really helping other users -- and they swear by it.

It's $80 thru Amazon (but you could return it if it doesn't work) --> https://www.amazon.com/MLA-30-Antenna-Active-Receiving-100kHz/dp/B07WFCTWDJ

It's only $40 thru E-Bay but you probably cannot return it --> 100kHz-30MHz Loop Active Receiving Antenna for MLA-30 Short Wave Radio US | eBay

The key is being able to put this somewhere in the open -- it MUST be away from anything metal and especially any houses, structures, etc. Trees are OK -- but one advantage is height isn't important. You can install it on a 6ft (non-metallic) pole.

If it works then it's a pretty good value.