Monday, August 30, 2010

Build a roll up portable 2m (144MHz) slim jim antenna

The "slim jim" antenna has a number of advantages over a helical or quarter wave:

  • It is quite broadband because of its folded element.
  • It does not require any ground plane radials because it is an end fed half wave.
  • It has more gain.

To make a portable one you will need:

  • a 1.7m length of 450 ohm twin feeder (sometimes sold as "ladder line").
  • some string.
  • two cable ties.
  • RG58 50 ohm coaxial cable or similar. Any length to suit.
  • coaxial plug to match your transmitter.

Here is how to build the antenna:

  1. Bare a section of each side of the twin feeder, fold over at 90 degrees and solder the two wires together.
  2. Measure down 151 cm, leaving a bit extra for the folding over and do the same so that you have a 151cm length of feeder shorted at each end.
  3. Measure up from the bottom 49.6cm
  4. Cut the wire on one side of the feeder here.
  5. Measure up 2cm and make another cut on the same side.
  6. Remove this 2cm piece of wire.
  7. Measure up from the bottom 10.3cm and bare the wires on each side of the feeder.
  8. Tin this wire with solder.
  9. Prepare end of your coaxial  cable so you have the inner and outer shield separated.
  10. Solder the coaxial to the feedpoint previously prepared. It does not matter which side of the antenna the inner and outer go to.
  11. Drill four holes either side of the coaxial just below the feed point through a solid part of the cable and secure the cable to the feeder with two cable ties. This makes it very sturdy.
  12. Fit coaxial plug.

Now you have a roll up 2m antenna. You can use the string to hang it from a curtain rail. You could even put it inside a plastic pipe and put it outside if you wanted to. It will roll up to put in your luggage.

To tune the antenna you would move the feed point up or down the open wire feeder, but I have made a few of these and found these dimensions give a good match. Another way to vary the impedance of the antenna is to change the size of the gap. I remember seeing a commercial slim jim with a moveable section there to allow tuning. Starting with a gap of 15mm and extending it till the match is perfect may be worth trying.

Thursday, August 12, 2010

New blog about Fundraising

This just a short note to say that I have set up a new blog solely to deal with my professional life in fundraising, marketing and voluntary sector management at

This should not have any effect on my existing blog as the new one is mainly comments on news stories covering fundraising and charity issues.

The new blog is hosted by Blogger (free of charge) and uses their  custom domain feature although the domain is registered through Blacknight rather than Google/Blogger. It also utilises the new Blogger static pages feature which allows up to ten static web pages for other non blog information. Its surprisingly good. Blogger now also has a version of Google Analytics built into it (currently only accessible through "Blogger in draft").

Total cost of setting up the new blog £0 as I already owned the domain name (less than £10 to buy if you don't already have one.

Tuesday, August 10, 2010

Making some slight changes to my blogging habits

Being a user of the Chrome browser by Google I was recently prompted to install the "blog this " extension. This puts a little blogger icon in my toolbar and allows me to add an article to my blog which links to any page I visit in my web browser. I promise to use this sparingly, but it might allow me to comment on some interesting articles and issues as I find them.

Friday, August 6, 2010

How to start promoting your business or club using Twitter and Facebook

One of the best ways to increase the spread and influence of your business is through social networking, especially Facebook and Twitter. I would recommend all businesses to have a Facebook page and a Twitter feed especially if they have regular news updates to publish. Its a convenient and cheap way to get that information to customers and it keeps you in their minds the next time they want something that you supply.

Both of these services use short status updates which can contain your message and a link to a related web page. If someone "likes" your Facebook page then your status updates will appear in their "most recent" or "top news" feeds. The position of it on the list may change if people are commenting on it. Twitter is slightly more haphazard as your update will appear chronologically in among the updates of everyone else your follower is following, but it is still a very good communication tool.

A personal user of Facebook and Twitter would probably not want the same status updates going to each feed, because a personal Facebook page is restricted to friends only with Twitter usually being public. A business, on the other hand, would probably want both accounts carrying the same news so there is an easy way to achieve this.

1. Create a Facebook page for your business (not a group).
2. Create a Twitter profile.
3. Go to and connect the two accounts.

Once this has been done any status updates you make to your Facebook page will automatically be sent out on Twitter with a shortened link to the original page on Facebook.

Be prepared to interact with users on both services by regularly checking and engaging in discussions and comment threads on Facebook.

Twitter has a number of third party automation tools which you will want to start using once you get more involved with it. One of these is which can do a number of clever things including sending a personal message autoresponse to anyone who follows you and automatically follow them back. This can allow you to grow your network without having to manually check and follow each new follower. Socialoomph can also be used to trickle feed updates automatically at certain times. 

If you have a blog then can send an update to twitter each time you add a new article. This can be useful in retaining engagement with customers.

This is just the start, but remember it is about building and engaging with a community of people who have similar interests to you. Whatever updates you send out, my advice would be to limit it to one in five of a commercial nature. The rest should be informational or people will just start ignoring you or not feel good about your organisation.