This antenna is amazing, super high gain, physically strong and good bandwidth (for a narrow band design antenna)

We just finished this antenna today, and straight off the bench and on to the SWR meter it was less than 1.5. We tweaked it a little with the tuning bar at the bottom and straight down to 1.0

This one is destined to Haiti to replace a 4 way stacked dipole that was destroyed in the recent Hurricane Matthew. For the first time we will be able to do a direct comparison with a four way dipole stack correctly spaced at 0.9 wave length, with the same geographic position and tower. These dipoles were in service for many years, so Mamasita has a lot to live up to and compete with.

What’s of great interest here is that all the simulation programs for antennas show that a four way dipole stack will out perform the double 5/8 co linear Mamasita, but the few real physical tests that we’ve made have not agreed with the simulations, this is going to be a great opportunity to really verify if indeed the Mamasita can really equal or even outperform the 4 dipoles.

We excitedly wait 🙂

We were asked recently by a customer in Haiti to make some coverage plots from a particular site in the south of the country from the side of a mountain. We’ve been doing these plots quietly for years. We make them by using NASA’s Shuttle Radar Topography Mission or SRTM data collected from a mission in the year 2000. NASA and the US Government kindly made this available for companies like ourselves to use 🙂

nasa-srtm

The Shuttle Radar Topography Mission (SRTM) was an international research effort that obtained digital elevation models on a near-global scale from 56° S to 60° N to generate at this time the most complete high-resolution digital topographic database of Earth. The data was collected using a specially modified radar system that flew on board the Space Shuttle Endeavour during the 11-day STS-99 mission in February 2000. To acquire topographic data, the SRTM payload was outfitted with two radar antennas. One antenna was located in the Shuttle’s payload bay and the other on the end of a 60-meter mast that extended from the payload bay once the Shuttle was in space. The technique employed is known as interferometric synthetic aperture radar.

Over the years we have made thousands of plots using this data for customers asking us the same and most popular question, “How much range can we get?” This data has enabled us to be able to predict the range and coverage to an accuracy of more than 90% and saved customers thousands of dollars in bad planning.

Back in 2009 the British Army had us making plots for the installation of radio transmitters in Afghanistan. At the time the Army engineer said to us, how do you do this? this is better than anything our tech guys can produce. Obviously we were flattered given the resources of the British Army and we duly continued making the plots for them.

We produce the RF coverage plot, then make a png overlay image file for Google Earth. Once in Google Earth we can tilt north, east, south and west and zoom in and out, it’s amazing.

This latest plot uses our 1600W ERP system in the south of Haiti in the Massif de la Selle mountain range. You can see the north view at the top of this post. Below are the views from the east, south and west.

Paul Hollings.

https://aareff.com/paul-hollings.htm
http://uk.linkedin.com/in/paulhollings

hosanna-jacmel-haiti-1600w-30m-east

hosanna-jacmel-haiti-1600w-30m-south

hosanna-jacmel-haiti-1600w-30m-west

Just had a call for a customer in the UK who wanted to know how to reduce the power of a 100W amplifier (same for a 100W transmitter) internally down to 70W to comply with OFCOMs licencing conditions. I said you can adjust the power internally, but there are some controls that you should never touch if you want to your amplifier to stay alive.

The picture attached to this post should help to clarify the purpose of each adjustment inside the amplifier.

Main Power Supply Power Adjustment
The main big 48V DC power supply is the best and recommended way to reduce the power. There is a little control at the front on the left hand side of it where all the cables connect. The power supply can be taken down to about 42V, this should reduce the power to about 70W with stability. If this is not enough, then DC Control board will need to be adjusted.

DC Control Board Power Adjustment
This control pot is marked FWD on the DC Control board. Only adjust this pot, DO NOT TOUCH THE OTHERS. This control is used to limit the amplifier to a maximum of 100W, it’s an AGC type control. With irresponsible adjustment this control can be adjusted so the amplifier does more than 100W, !!! DO NOT DO THIS !!!. It will work at more than a 100W for a while, maybe a day, maybe a week, maybe a month, but then it will die, so please don’t do it. You can adjust the power anywhere between about 10 and 100 watts with stability on this control. If you damage the amplifier through misuse of this control it will not be repaired under warranty

Other Controls Marked in Red
The other controls marked in RED should not be touched, these are factory set and are there for the sole purpose of protecting the amplifier against reflected power and over temperature. If they did not matter or were not needed, we would not have designed them and put them there, so please tread carefully. If you damage the amplifier through misuse of these controls it will not be repaired under warranty.

Paul Hollings

http://uk.linkedin.com/in/paulhollings
https://aareff.com/paul-hollings.htm

It came to our attention recently that little town of Dajabon in Dominican Republic has a international market every Monday and Friday where the border is completely open, no restrictions, just walk through with goods backwards and forwards all day long. The following video is worth watching and explains all this and how the people in this area of the island get along and how the European Union changed and improved the lives for these people with proper management of free trade.

We have customers that we know of in Haiti in the cities of Jacmel, Carrefour, Port-au-Prince, Saint Marc and Cap Haitien. Over the last few years some customers have visited us for service, sales, advice and repair of equipment. If you don’t know, we Aareff, are based in Santiago De Los Caballeros.

Always when our customers from Jacmel and Port-au-Prince take the south route via Barahona and and Santo Domingo they have problems at the border crossing. On the way into Dominican Republic they are always asked for a mountain of documentation to allow crossing with the equipment and if they don’t have this, they are asked to pay a fee, usually without any official receipt. If that wasn’t enough, when they return to Haiti the same route, the same happens at border crossing going the other way. The Haitian officials pull the same stunt.

One of our customers in the Cap Haitien area takes the north route and actually has a friend based in Santiago that makes the trips for him. His friend shared the experience with us and said that quite simply on a Monday and Friday in Dajabon you just walk straight across the border with the equipment, there’s no hassles, no questions, no legalities, and no demands for money, the border is open for free trade. This is the only part of border between the two countries that is like this.

In conclusion, if you are based in Haiti and you want to visit us to buy equipment or return with equipment it is worth pursuing the more usual northern route. Maybe we can talk to our customers friend in Santiago and he will make the trip for you for a small fee, it’s possible.

Let us know. 🙂

If you find yourself in possession of an old 100W transmitter that has burnt out, there is light at the end of the tunnel and a high possibility it can be repaired. The one featured here was not looked after very well, dirt, sand, grime you name it had entered the fans and never been cleaned, this caused the fans eventually, after years of continuous use, to cease.

No Fans, No Cooling + Hot Part of World = Components Melted 🙁

The most common component from the 2010 model to fail from overheating was the output filter trimmer capacitors. In a later design change we successfully replaced these trimmers with a stack of fixed chip capacitors to make the amplifier block even more robust in temperatures of +40C.

If the transmitters is in a real mess, full of corrosion, been dropped and bent and generally had a hard life or unskilled engineers or techs have been in there and pulled it apart without knowing of what they’re doing, then it’s days are probably numbered.

If the general condition of the amplifier is good, not too rusty, battered or falling apart, you are handy with a screwdrive and a little electrical knowlege, then it is worth fixing by sending the internal modules back to us, we fix them, then send them back to you for re-installation.

BEFORE DOING THIS PLEASE CHECK THE FOLLOWING

Follow the notes on the picture at the top of this page. Check the:

  • Main transistor on the PLL drive board is quite warm, this is a fair indication that the unit still has drive power
  • 2 way DC terminal block on the main amp block in front of the fan for 48V DC. If you don’t read 48V DC, then carefully remove the red wire from the block, take care it cannot touch ground, the chassis or any other connection and then check the red wire for 48V DC whilst it’s disconnected.
  • 3 way DC terminal block on the amplifier block for 15V DC

If these 3 things are still okay, then take a clear picture of the top of the transmitter, just like the picture here, on the highest resolution you can, email it to us at info@aareff.com and we will send you a price quotation for the repair. It will normally cost three hours of our labour. If the MRF151 main transistor has burnt out, then you will need to pay for that. It is not always the case that the MRF151 has burnt out, quite often it is still intact. The repair will include the upgrade of the 100W AMP BLOCK with the chip capacitors and checking all the other boards.

IF YOU AGREE WITH THE REPAIR QUOTATION THAT WE SENT TO YOU, THEN REMOVE THE MODULES AND SEND THEM BACK TO US

Please follow the instructions in the picture below to remove the 4 modules.

repairing-melted-trimmers-on-old-100w-transmitter-2

When you have the 4 modules out of the enclosure

  • Pack the 4 modules into a box with plenty of soft padding around the top of the amp block. The parcel should only be fairly small and less than 2 Kg / 4.4 LB which means you can use small packet registered or certified airmail, this keeps the cost low
  • Print out the commercial invoice that we sent with the quotation and put it on the outside of the parcel so that customs officials can see it
  • Take it to the post office and send it to:
    AAREFF SYSTEMS / PISANO
    AUT JOAQUIN BALAGUER
    SANTIAGO
    51074
    DOMINICAN REPUBLIC
  • Email us the tracking number

When the parcel arrives with us, we will let you know.

The guys have been working hard here this time bringing a long overdue Aareff transmitter with a digital frequency display.

This all came about as we decided to design an all in one enclosure 200W Stereo FM Transmitter. The previous 200W Transmitter models have all been 1W Driver Exciters and 200W Amplifiers packaged together to make 200W Transmitters. During the design, we thought, hey we’ve come this far, let’s package a frequency display in too.

At the moment the the MPX version and the Stereo Version of the 200W transmitter are available with or without the frequency display. We intend to bring you a version with the audio processor and limiters included later this year.





Friday the 5th of August, we celebrated 5 years of Aareff in the Dominican Republic.

As a treat to the amazing and loyal staff we decided to take the day off from building and selling transmitters and go to one of the best beaches in the world, the north coast of Dominican Republic. We ate good food, fresh fish, drank the Dominican beer Presidente. The went on to bask in the sun, build sand castles and swim in the Atlantic Ocean all day.

We want to say to our workers, our customers, the courier DHL and the Dominican government a BIG THANKS !!! for helping us make this happen.

We are now giving a customise option to anyone that buys a new transmitter from us! This is a special order for a 200W transmitter that we made for one of our customers to include a 7-16 high powered RF connectors and XLR audio connectors on the rear panels. Let us know what you think of this and what other personal customisations you may find useful for when you order your next or first transmitter.


Hosanna Radio started of as a small community radio program for the locals in Jacmel, south of Haiti. Using our equipment they are now the most popular radio station in the region. All this is since 2011.

It was a challenge keeping them on air at first due to the high level of sand and salt in the air, not to mention the corrosive effect it had on the circuits. With a careful redesign in the critical areas of the circuitry, we were able to overcome these problems and provide a first class service maintaining a 24/7 broadcast. They are so satisfied with our service and equipment that they want to upgrade to a second transmitter in the mountains due to there increase in popularity.

2014-10-13_haiti_jacmel-marigot_health-70

They use the 1000W ERP system, this is two 200W amplifiers combined to give 400W with a two way stacked dipole antenna. If you want more information on this click here or you can buy here.


Always nice to see customers upload their videos of their stations and how they use the equipment. Big big thanks !! to ‘shamuutube’ and keep up the great work 🙂

This is the 30W transmitter complete with audio processing / limiter. You can find more information on this at http://www.aareff.net/30w-stereo-fm-transmitter-audio-processing, email us at info@aareff.com or you can purchase directly here.