2 antennas: Same model, different characteristics

Hi there! Some of you may remember that I used a RH-770 antenna for my handy-talkie. I found out that the one I had been using was a imitation. So, I obtained a Diamond brand RH-770 antenna from Blazer Electronics Center in Sim Lim Tower. That being said, if you are in Singapore or manage to get a chance to come, you should visit the shop one of these days!
It is located at the basement, for your information.

So, here are the 2 antennas side by side. Can you guess which one is the imitation? πŸ˜‰

 

 

 

 

 

 

 

 

So, Mr Jeff used his Anritsu Site Master to test the performance of the antennas. Here are the results of the imitation antenna.

VSWR plot:

 

 

 

 

 

 

 

Smith Chart:

As you can see, the imitation antenna is good on the VHF band but it doesn’t perform as well on the UHF band. What about the Diamond RH-770? Here are the results.

VSWR plot:

 

 

 

 

 

 

 

Smith Chart:

 

 

 

 

 

 

 

So, the old saying is true, you get what you pay for! The Diamond RH-770 works well on both VHF and UHF bands! Definitely will recommend people to get this antenna for their handy-talkies if I can.

Anyway, thanks for taking your time to read my blog!

73,
Joyce Ng (9V1AN)

A new year, a new beginning

Hi there! I haven’t written anything since last year, so that being said, Happy New Year! =)

Its almost a year since I got involved in the hobby of amateur radio. So, what are my plans for this year?

Firstly, I’ll continue to do all sorts of experiments like what I have been doing, and of course, you’ll get to see them here! =)

Secondly, I’ll be giving presentations at SARTS, and hopefully, at schools like my secondary school so that I can introduce youth to the hobby of amateur radio. I’ll be doing a few technical presentations this year. Hope that I can impart some of my knowledge to everyone!

Thirdly, I’ll be organizing or helping out with events such as field day in Singapore and maybe set-up temporary radio stations at schools for students and the general public?

This year will definitely be packed with various events. Hope to be able to learn more things about radio this year!

Thanks for reading!

73,
Joyce Ng (9V1AN)

Repeater antenna tuning — A sad but interesting find

Hi everyone! A few days ago, I was told that the antenna meant for use with the new repeater had a few tuning issues. They just couldn’t get the antenna SWR for the 2 meter band to be lower than 2. Feeling ambitious enough, I decided to try tuning the antenna with my friend, Yong Quan.

This is a picture of the antenna.

 

 

 

 

 

 

 

 

 

So, we laid it down on the floor and started to move sections of the antenna up and down toΒ  try to tune it. Here’s the original VSWR plot before we started.

 

 

 

 

 

 

 

Doesn’t look too good for the 2 meter band, ain’t it? We moved sections of the antenna up and down, and even removed some of the radials of the antenna to try to isolate the problem. We removed the feed point from the bottom half of the antenna, leaving only the top part of the antenna connected to the feed point, like this:

 

 

 

 

 

 

This is the VSWR curve now:

 

 

We got a SWR of 2.6! That still isn’t good, even though it decreased. We suspected something was wrong, and we removed the top section of the antenna from the feedpoint, leaving only the feedpoint.

 

This is the set-up:

 

 

 

 

 

 

 

 

 

 

And this is the SWR curve:

 

 

 

 

 

 

 

The SWR curve looks just about the same! And do you realize something? The
lowest dips in SWR are frequencies off our target frequencies! In fact,
we found that the antenna has a fixed resonant frequency around 133 –
135 MHz, which is around 10 MHz off the 2 meter amateur radio band
allocated to us! What in the world is going on here?!?

We decided to unscrew the cover of the feed point. This is what we got:

 

 

 

 

 

 

 

 

 

 

Yup, a tuned LC circuit. Apparently, they tried to make the antenna resonant only at a specific set of frequencies using this tuned LC circuit. However they are off by quite a lot.

Well… I feel for the person who bought this antenna. It cost more than SGD $400. This was a sad, but yet interesting and informative find.

Anyway, thanks for reading my article!

73,
Joyce (9V1AN)

9V1RS – Singapore local VHF repeater finally up

Hi there! Our local repeater has been down for a pretty long time now. Yesterday, I was at Mr Jeff’s lab to help with testing the local repeater.

The repeater will be relocated to its permanent location soon. In the mean time, it would be located at his office. For now, here is a picture of the antenna that would be used at the repeater’s permanent location.

 

 

 

 

 

 

 

 

 

When Mr Jeff received the antenna. He must have had a huge shock. Why? Because this happened:

 

 

 

 

It has been bent back into shape,
but its still dented a lil’ bit.

 

 

 

 

Anyway, thanks for taking the time to read my article!

Regards,
Joyce (9V1AN)

SARTS Presentation: What I have done in amateur radio since I obtained my license

On the 27th of November, 2014, I gave a presentation at the Singapore Amateur Radio Transmitting Society titled: “What I have done in amateur radio since I obtained my license”

Here is the video for those who are interested:
I apologize as the camera work wasn’t good.

Anyway, thanks for taking the time to read! πŸ™‚

73,
Joyce (9V1AN)

Got a new HF rig!

Hey there! I apologize for not posting for so long, I was busy for the past few months so I haven’t be able to post as much as I would like to.

And, after a few months, I finally got myself my own HF radio transceiver, from a person named Mr
James Brooks, 9V1YC. He sold me a Kenwood TS-930 for S$550. Thanks a lot, Mr James! =)

This radio, as what Mr James says, “was (and still is) considered one of the best receivers ever
designed.” I guess, when I do use it, I will find out for myself if that is true or not. πŸ˜›

According to the technical specifications, this radio has a output power of 250W max for SSB and 80W max for AM modes.

Here is the radio on my desk:

 

 

 

 

 

 

 

Now, I just need a proper antenna before I can send or receive anything. I guess, I will try to settle that in a week or two.

By the way, I’d like to thank a friend, Dylan for helping me take the radio back home. I wasn’t able to carry the 18.5KG mass that this radio had. >.<

Thanks Dylan! Wow… I didn’t expect to be up with a rig that fast. Thanks a lot to Mr James, Dylan, and also Mr Jeff, for sending out the offer to everyone! =)

Now, I have something more to talk about for next month’s presentation! I am feeling nervous though! πŸ˜›

I guess, when I do finally get the antenna system up, I would write an article! ^.^

Anyway, thanks for reading!
Joyce (9V1AN)

Experimenting with a TV Yagi Antenna

Hi, sorry for not posting for long. Guess what? I got my hands on a 12 element Yagi antenna used for TV reception.

I was at Mr Jeff’s lab testing out the transmit performance of a TV Yagi antenna when compared to a Yagi antenna made for the amateur radio bands. The antenna didn’t have a proper connector so we just used a few crocodile clips to connect it to the antenna analyzer.

This is the performance of the antenna when connected up to antenna analyzer. Note that this configuration is mismatched as we connected a cable of about 50 ohms impedance to a 75 ohms impedance antenna.

I am really surprised by the results! For the 70 centimeter band, the SWR of the antenna is around 1.8 to 2. Even for the 2 meter band, the SWR of the antenna is around 2.6. Some tuning and matching would make it better! :)Now, let us compare our results to a Yagi antenna built specifically for the 70 centimeter and 2 meter bands. This is the antenna itself.

And here are the results of his antenna:

Of course, you get what you pay for! Mr Jeff’s antenna has an SWR of 1.23 for the 2 meter band and 1.04 for the 70 centimeter band. But hey! For a S$30 TV Yagi antenna, as compared to a S$170 dual band antenna, its performance is really not bad!It was fun learning working with antennas, I’ll see whether I can tune and match the TV antenna to get the maximum efficiency possible, that is, if I have the time! πŸ˜›

Well, thanks for reading and enjoy your day!
Joyce (9V1AN)

My thoughts on engineering

Hi, my apologies for not posting something for quite a while. Well, I am not going to write about radio for this post, however, I’d like to share with you my thoughts on engineering.

So, what does engineering mean to you? To me, engineering is a form of art. Why? You ask, why do I think so?

Engineers can take individual parts and components, each with their own separate function, combine the parts together to create a useable, working system. To me, the idea that understanding how the different parts work, to make a system of individual components that work together in unison, to serve a practical purpose, intrigues me, even to this day.

Before we even build anything, be it electrical or mechanical, how do we know how to go about building it? We follow or draw a mechanical or electrical drawing and build a device based on those drawings. We then gather all of the required parts together, combine them according to the drawings and make it work!

If you think about it, isn’t the electrical or mechanical drawing a form of art? Look, an engineer can draw out his/her system as a drawing, and other engineers can understand what the device in question does! Isn’t it an expression of the thoughts and the ideas of the engineer who designed the device?

In art, math plays a part in determining how the final picture would look like. Circles, squares, parabolas, sinusoids can be expressed and described using mathematical equations. In radio, one thing that makes me wonder is that how does changing the shape, adding another antenna element, or even varying the height change the characteristics of the antenna? What about its shape changes that? That is something I would want to find out when I make the time to do so.

So, I question, don’t you
think engineering is a form of art? Can’t we look at engineering from
that perspective, instead of viewing engineering as a technical field of
work? Opinions?Anyway, thanks for taking the time to read my blog!

73,
Joyce Ng (9V1AN)

Approaching youth on Amateur Radio

Hi, I noticed that in Singapore, there are very little youth that are into Amateur Radio (Wait, I seem to be the youngest when I go to the SARTS meeting! :P).Β  I have been asking myself over, and over again: “How can we bring in other youth into amateur radio?”

I guess, firstly, we must try to understand what other youth think about radio technology. If you have read some of the previous articles I have written, you would have realized that in some of my articles I put statements about what other people, especially youth, tell me in regards to what they think about radio.

I think we should make people understand that radio technology is not outdated, but is actually growing. We should show the relevant real life examples to how and where radio is used, so that to get people to think about how and why things work, and maybe spark the interest of some people.

Secondly, I believe that if we decide to learn anything, we should learn something that can be applied. As you all know, to become a radio amateur, you need to pass an electronics exam. But yet, some people just buy off the shelf rigs and use them, with little to no application of whatever theory they have learned. The question that I would like to ask is, how do we give a little more emphasis to building things? When we were young, most of us would ask, why does a television set work? Why does a radio work? I still ask these type of questions, and it is in my nature to tear things apart to try and find out how things work. As I mentioned in my first point, we must interest people in the way that makes them want to find out how and why things work. Then we can build devices to allow people to apply whatever the have learned.

And finally, we shouldn’t just ask and tell people to get into the hobby. Rather, show people a practical device. And then ask people why do they think the device is able to work. I believe that when it comes to technical subjects like radio, when you can make people question why things work, to the point that they are much willing to find the answers for themselves, you have already won the battle. I believe the internal motivation and interest is the best way to get anyone into any subject.

What do you think? Please feel free to write your comments. Anyway, thanks for taking your time to read my blog!

Joyce Ng,
9V1AN

Setting up a fish pole antenna

Hi there, well, last Thursday, I was with Mr Frankie and Mr Jeff at Mr Jeff’s workplace, and we set up a double bazooka antenna, using a fish pole as a mount.

Here are some pictures of the antenna set up:

 

 

 

 

 

 

 

This is Mr Frankie and myself setting the thing up:

 

 

 

 

 

 

 

This is everyone who were there to help out:

 

 

 

 

 

 

 

 

This is Mr Frankie’s portable rig setup:


 

 

 

 

Can you imagine? A Yaesu FT-857D, being powered by a 12 volt lead acid battery, and Mr Frankie is still speaking to people in the Philippines at 100 watts of power? And the thing lasted nearly an hour? It is certainly impressive, that the whole setup there, excluding the cables, can be placed into a medium sized bag. This coming Saturday, some members of SARTS will be organizing a DX event to try to communicate with people all around the world. I will keep you updated of what is happening.

Anyways, thanks for taking your time to read my blog!
73,
Joyce Ng