RPA-1 Preamplifier User Manual
Contents
1. Its unique combination of push pull design and robust components provides significantly better performance than other preamplifiers on the market so we know you are anxious to get started Before you install the RPA 1 take a few minutes to read this brief user guide and familiarize yourself with the installation operation and safety procedures We are confident that you will find this preamp easy to use and that it will reward you with years of faithful service Additional Requirements Please note you will need the following items not included in this package to install and operate the RPA 1 receiver preamplifier Power Source The RPA 1 requires a negative ground 10 18 Vdc 200mA min power source that is not included Depending on the supply current you might also need an inline fuse Powering the RPA 1 through the coax feedline requires a voltage injector circuit or a DX Engineering FVI 1 Voltage Injector that includes a power supply Refer to Connecting the Power Supply on page 9 for details Sealant If you opt to mount the unit outdoors you will also need a silicon based sealant such as 100 pure silicone RTV DX Engineering part number RTV598335 Refer to Installation and Maintenance at the top of page 8 for complete information Page 4 RPA I User Manual Specifications he specifications in the table below represent typical performance from the RPA 1 preamplifier Power Requirement 10 18 Vdc 140 mA maximum Ou2. To reduce gain cut a lead from C3 and C6 See page 9 To reduce gain sol der a 1500 resistor in parallel with R1 A and another with R6 Unsolder RFC1 lead that con j S 9 Dee page nects to power jack and then reconnect to center pin of the To reduce gain sol RF output jack See page 9 der a 1500 resistor in parallel with R1 and another with R6 See page 9 X To reduce gain cut a W lead from C6 and C3 T See page 9 Figure 3 Circuit board illustrates how to reduce the gain and power the unit through the coax Maintenance The RPA 1 requires virtually no maintenance as long as the unit is not exposed to direct sunlight moisture or extreme temperatures But as with any electrical device lightning is a concern Lightning While most amateur radio operators rarely suffer damage from lightning even though they never disconnect their equipment the best protection is to disconnect electrical devices during storms The key to proper lightning survival is proper grounding of feedlines and equipment and maintaining integrity of shield connections A proper installation improves lightning protection and enhances weak signal receiving performance Consult lightning protection and station grounding information in the ARRL handbooks the NAB Broadcast Handbook or other reliable sources RPA I User Manual Page 3 Introduction ongratulations on your purchase of the RPA 1 receiver preamplifier
3. WARRANTY Wanay tt ieee ane d ae te catego eae vee dese A E A ES 12 Warranty Technical Support f you have questions about this product or if you experience difficulties during the installation contact DX Engineering at 330 572 3200 You can also e mail us at DX Engineering DXEngineering com For best service please take a few minutes to review this manual before you call Warranty All products manufactured by DX Engineering are warranted to be free from defects in material and workmanship for a period of one 1 year from date of shipment DX Engineering s sole obligation under these warranties shall be to issue credit repair ot replace any item or part thereof which is proved to be other than as warranted no allowance shall be made for any labor charges of Buyer for replacement of parts adjustment or repairs or any other work unless such charges are authorized in advance by DX Engineering If DX Engineering s products are claimed to be defective in material or workmanship DX Engineering shall upon prompt notice thereof issue shipping instructions for return to DX Engineering transportation charges prepaid by Buyer Every such claim for breach of these warranties shall be deemed to be waived by Buyer unless made in writing The above warranties shall not extend to any products or parts thereof which have been subjected to any misuse or neglect damaged by accident rendered defective by reason of improper install
4. Page I2 RPA I User Manual RPA I User Manual DX ENGINEERING RPA 1 Preamplifier User Manual DXE RPA 1 INS Revision 0 PATENT PENDING ODX Engineering 2004 P O Box 1491 Akron OH 44309 1491 Phone 800 777 0703 Tech Support and International 330 572 3200 Fax 330 572 3279 Email DXEngineering DXEngineering com Page 2 RPA I User Manual RPA I User Manual Page Il Table of Contents INTRODUCTION Additional Requirements 000 000 0 ccc cece eteeteeeteeeseteeneenn 4 SPECIFICATION Specifications Glossary cece cee ce cece cece steeessetecseeaeen 5 Third Order Intercept cece cee cecteceecseecsetessesseteeseesenn 5 THEORY OF OPERATON Special Features of the RPAC1 0 000 ccc eeeeeen 7 INSTALLATION AND MAINTENACE MOUNUNO cerea E E E S 8 Mounting at the antenna c ccccccssscscscsceesesesesssssescscsescacscecaceneseneesiestseseaeaeaes 9 Determining the sensitivity cccccccccccscssssssesssesescscscecececesesesessscesscseseacseaeesaes 9 Connecting the power SUPDIY cccccscsssscsssescscscececesesesessscsescscsescsescseacetaneneeeees 9 Powering through the COaX cccccscecsceesesesssesessseseacsescerecesesesesesessscssseseecaceeens 10 Reducing gain oo cccseccsesssscsesesssessscssesesesasesesessssssssssssasasasaeraeiessisitisetscseseaeeeaes 10 Maintenance 0 ccc cc ccececneenessecseeesseeessessesseeeeseseessesaeeeseesseseeeatens 11 LIQHtning O 11
5. arrel type plug included A traditional 500 mA or larger wall wart with 12 Vdc negative to shell plug wiring is generally adequate for powering the RPA 1 You can also use a larger regulated supply provided it supplies 10 18 Vdc negative ground has the power plug shell connected to negative and has an inline 1A fuse WARNING Be sure the supply polarity and voltage are correct Powering through the coax The external power connector is normally active but components are inside the RPA 1 to allow powering through the coaxial feedline To change the power feed refer to Figure 3 at the top of next page and do the following Caution Do not nick scratch or break the fine wires on the choke Do not grab the choke body with pliers 1 Unsolder the 100 uH RF choke lead that connects to the power jack 2 Connect the free choke lead to the PC board indicated by the choke outline NOTE A 12 18 V dc positive power source must be inserted in the feedline center conductor through a similar 100 uH choke and the voltage must be blocked from appearing at the receiver A DX Engineering PV1 1 voltage injector which includes a power supply can also be used Reducing gain If signals are overloading your receiver or if background noise is excessively high there are two solutions The first solution involves adding a conventional attenuator pad either leading or following the RPA 1 Addition of a pad on the input will reduce noise figure ro
6. ation damaged from severe weather including floods or abnormal environmental conditions such as prolonged exposure to corrosives or power surges or by the performance of repairs or alterations outside of our plant and shall not apply to any goods or parts thereof furnished by Buyer or acquired from others at Buyer s specifications In addition DX Engineering s warranties do not extend to other equipment and parts manufactured by others except to the extent of the original manufacturer s warranty to DX Engineering The obligations under the foregoing warranties are limited to the precise terms thereof These warranties provide exclusive remedies expressly in lieu of all other remedies including claims for special or consequential damages SELLER NEITHER MAKES NOR ASSUMES ANY OTHER WARRANTY WHATSOEVER WHETHER EXPRESS STATUTORY OR IMPLIED INCLUDING WARRANTIES OF MERCHANTABILITY AND FITNESS AND NO PERSON IS AUTHORIZED TO ASSUME FOR DX ENGINEERING ANY OBLIGATION OR LIABILITY NOT STRICTLY IN ACCORDANCE WITH THE FOREGOING DX Engineering 2005 DX Engineeringe DXE Hot Rodz Maxi Core Antenna Designer Yagi Mechanical and Gorilla Grip Stainless Steel Boom Clamps are trademarks of PDS Electronics Inc No license to use or reproduce any of these trademarks or other trademarks on this web site is gtven or implied All other brands and product names are the trademarks of their respective owners RPA I User Manual
7. e much background typical production RPA 1 noise to the system If the feedline loss is high performance might improve with the ais sa third order preamplifier mounted near the antenna ais a The RPA 1 is significantly e Small loops magnetic loops These antennas also lack sensitivity and may require more immune to overload mounting the amplifier near the antenna when cable runs are lossy than the best commercial amateur receivers Third l ini itivi order products are 50 dB 3 _ eee aoe A Ey a ae STARTES RA a0 Euz ven so enz uP 30 0 ate The following is a simple method to confirm adequate sensitivity This test generally requires the and E ae assistance of another operator Figure 1 A typical third order intercept of the RPA 1 1 Listen at the quietest expected operating time with the receiver set to its narrowest selectivity 2 Remove all receiving antennas from all feedlines 3 Replace the antennas with a resistor load of the same impedance as the antennas 4 When the load is substituted for the antenna a noticeable decrease in noise should occur It is advantageous to have receiver AGC action begin just above noise floor while avoiding excessive levels of background noise This usually occurs when there is a perceptible increase in S meter reading when the antenna is connected If background noise is high or your receiver is overloaded you can add an attenuator pad or remove power from the RPA 1 Removing power bypasse
8. kup The location of the amplifier rarely makes a difference in feedline noise Most feedline noise couples back to the antenna at the antenna terminals it does not leak directly into the feedline
9. s the RPA 1 Connecting the power supply The RPA 1 requires a well filtered 10 18 Vdc source with a negative ground A wall wart or station power may be used but must have an inline 1 or 2 ampere fast blow fuse 1f the supply is capable of providing more than 1A of current Place the fuse at the power supply rather than at the RPA 1 Page 6 RPA I User Manual Theory of Operation he RPA 1 is a high performance broadband LF and HF receiver preamplifier that features exceptional immunity to overload It also has a low input SWR and an excellent noise figure The amplifier is constructed of quality components mounted on a sturdy G 10 fiberglass circuit board The circuit board mounts in an aluminum enclosure suitable for indoor or outdoor use RF connectors are RCA phono and type F CATV fittings Performance is optimized for 350 kHz to 35 MHz where dynamic range and third order intercept are typically more than 20 dB one hundred times better than conventional preamplifiers Special Features of the RPA 1 Powered by 10 18 Vdc through the coax enabling remote operation at the antenna or to the 2 1mm connector e Push pull operation eliminates harmonic distortion e High quiescent current increases ability to handle strong signals without distortion or overload e RCA phono and CATV F fittings ease installation e Simplified switching automatic bypass eliminates gain when dc power is off e Meticulous craftsmanship and d
10. tput TOI Third Order Intercept 43 dBm 13 Vdc Noise figure 3 5 dB One dB Compression 26 dBm 4 watts output Gain 16 dB from 300 kHz to 35 MHz 1 5 to 1 5 dB over this range 500 Hz BW IM3 Dynamic range 110 dB or greater Specifications Glossary The following are simplified explanations of the specifications highlighted in the table above Third Order Intercept A standard measure of how well a receiving system performs in the presence of strong nearby signals The higher the third order intercept TOD the less likely adjacent strong signals will cause interference The RPA 1 offers substantially improved TOI over competitive preamplifiers and communication receivers Noise Figure The ratio of equivalent noise power developed at the input to that generated by thermal noise in the source resistance usually expressed in decibels If it were possible a perfect amplifier would have a noise figure of 0 dB The RPA 1 is extremely quiet and does not contribute noticeable noise to receiving systems Dynamic range The ratio of the faintest signal detected to the loudest signal amplified without significant distortion typically expressed in decibels The RPA 1 allows you to hear faint signals in the presence of adjacent strong signals Gain The ratio of signal input to output The RPA 1feautures a high gain that is easily reduced if not needed RPA I User Manual Page 9 The RPA 1 power connector uses a standard 2 1mm b
11. ughly by the amount of the attenuation This is usually not a problem with modest antenna efficiency At the same time noise figure decreases input intercept overload limits will increase Addition of an attenuator pad on the RPA loutput reduces output intercept Input intercept and noise figure remain essentially unchanged As a general rule reduction of gain with a pad at either spot will not compromise system performance This is because the RPA 1 design has a very large performance margin in both noise figure and intercept You can also reduce gain about 3 dB from 17 to 14 dB by cutting one lead of C3 and C6 Since this is a push pull circuit both capacitors must be removed See Figure 3 on next page If additional gain reduction is still necessary solder a 1500 ohm 1 4 watt resistor in parallel with R1 and another in parallel with R6 to reduce the gain to 10 dB Be aware internal gain reduction modifications will cause the upper frequency performance to fall off at approximately 15 MHz or higher Page 8 RPA User Manual RPA I User Manual Page 5 Mounting at the antenna Third Order Ordinarily the preamplifier should be mounted at the operating position rather than at the antenna There are a few exceptions however including Interc ept mle wie e Pennants flags and K9AY loops in quiet locations These antennas have relatively low Figure 1 below illustrates a sensitivity or gain When used in quiet locations they do not provid
12. urable components provide superior dynamic range RPA User Manual Page 7 Installation and Maintenance or best results mount the RPA 1 in a well ventilated area away from direct sunlight and moisture Constant operation in ambient temperatures above 150 F 65 C will shorten the life of the RPA 1 and should be avoided It is acceptable to mount the RPA 1 outdoors if the upper seams of the box are sealed with an outdoor silicon RTV sealant or coax seal Lower gaps or seams must be left open to allow condensation drainage Mount the flanges of the box flat against a horizontal surface or with the two mounting flanges positioned in a vertical line as shown in Figure 2 below Warning Never transmit through RPA 1 The unit can be damaged by direct application of transmitter power greater than I watt Mounting Optimum electrical location of the RPA 1 varies with antenna system backeround noise level A good receiving system requires the antenna to establish system noise rather than amplifying devices One common o myth is that preamplifiers must be mounted at or near antennas to be effective This is not true at VHF and lower frequencies unless feedline loss is high and the Power connector down Ey antenna has very low background noise Another eee E eee eayeeemne common misconception is that mounting at the antenna Figure 2 The RPA 1 can be mounted vertically or horizontally feedpoint reduces feedline noise pic
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