Help needed to make FM aerial work

S Bibby

Active Member
Hi,
I am trying to connect an FM aerial to my tuner which has a binding post-type of connection (several actually). I purchased a dipole FM antenna with coaxial socket (female) but forget to check if the tuner had a coaxial plug, which it doesn't. I then bought some coaxial plugs (male and female) and a length of coaxial cable from my local electrical shop.

What I wanted to do was connect the FM aerial I bought to my tuner using the coax cable. The guy at the electrical shop told me to strip away the braiding (shield conductor) and only use the core conductor without allowing it to touch the braiding. I have done this but at the same time managed to strip away the insulator in between the two copper conductors as well. Is this alright to use?

Just to make things clear - I hope to connect the core of the coaxial cable to the FM post, then do the same to the other end but fit a coaxial plug which will then go on to the FM aerial/antenna. I am a bit concerned as this is the first time I have touched coaxial and my Dad said that he always kept the braiding on before he attached the plug (for TVs I guess). When I explained my problem to the electrical shop owner he said that I must strip off the braiding because it is not needed and will otherwise short the connection out. I am not sure if he meant to do this just to the binding post connection (Tuner), or to both this and the coax to coax (Aerial).

Edit: I think I should add I am either going to wrap the coax around the FM binding post or perhaps attach with a screw/lug terminal.

Sorry if this sounds convoluted or confusing but I just wanted to get this sorted. Plus if it doesn't work I suppose I will need to find another aerial for FM/MW.

Cheers, Simon
 
Last edited:

S Bibby

Active Member
Actually I misunderstood what my Dad said - he separates the copper braiding then stuck the coax plug clip on top of it. I think it is the connection to the post which is troubling me - I have no braid left but I think I need a bit of insulator at the bottom to make sure it doesn't touch the core. Plus I have read that there is a difference in ohms (75-300) between some of the connections. One on my tuner is marked for 75 plus there are twin with 300.

Would this be a simpler solution? - http://www.maplin.co.uk/Module.aspx?ModuleNo=5145&TabID=1
 
Last edited:

Chris Muriel

Distinguished Member
Yes, the 4:1 balun (balance to unbalance transformer) will convert a 300 ohm ribbon type feed to a standard 75 ohms coax one.
Then use your coaxial cable with standard TV type IEC (aka Belling Lee) connectors).

Chris Muriel, Manchester
 

S Bibby

Active Member
Thanks for your reply Chris,
In that case I think I will need some of this ribbon wire to connect to the Balun. I know there are ribbon type aerials available but for some reason I thought the one with a coax connector would be better..

Just to clear things up, can I connect a coaxial cable (core only) to the 75 ohm FM post on my Tuner? There is definitely no coax plug/socket available.
 

Chris Muriel

Distinguished Member
I would love to see a picture of the connector area (or a manual) for your tuner.
75 ohms is normally unbalanced - and requires a coaxila cable connection.
300 ohms is balanced and uses ribbon cable.
Normally you would connect caox to your ariel (inner and outer) and the same inner and outer to your 75 ohm inputs on the tuner.

Chris Muriel, Manchester
 

S Bibby

Active Member
Hi, the tuner is a Marantz SR-320L -

Marantz ST320

I can honestly say there are 4 binding posts on the rear and nothing more -

1) FM - 75 ohms
2) FM - 300 ohms
3) FM - 300 ohms
4) AM

I also have a Technics Tuner with the same layout, the only difference is that the 75 ohms is labelled 'GND' which I believe stands for ground. I think I know how to wire coax to coax now but have no idea what I am supposed to do with the 75 ohm connection.
 
Last edited:

Chris Muriel

Distinguished Member
That does not give me a picture of the rear connections and I couldn't find a user manual on the Marantz website; all I found was an expired Ebay auction for it (possibly you were the purchaser) with no rear view picture.
The FM 75 ohms input should not need a balun if connected to an FM antenna that has coaxial cable connections.
Just try connecting it up and see what happens; if screen and earth to terminal posts A and B doesn't work, reverse the connection - it can't do any damage.

Chris Muriel, Manchester
 

S Bibby

Active Member
Hi,
Just to update this I have ordered a twin lead from Ebay which I think is identical to the other own I bought except it lacks a coax plug. I will update this post if all goes well anyway, thanks again for the help Chris.

Edit: Twinlead cable is working fine now, I will hang on to the coax one until I find a better solution.

Regards,
Simon
 
Last edited:

The latest video from AVForums

Podcast: LG C1 OLED First Thoughts + JBL Synthesis SDR-35 Review, TV Show & Disc Reviews & more
Subscribe to our YouTube channel
Support AVForums with Patreon

Top Bottom