hy-qain 644 Footwarmer Amateur Radio Amplifier Owner’s Manual
- June 1, 2024
- hy-qain
Table of Contents
hy-qain 644 Footwarmer Amateur Radio Amplifier
Specifications:
- Height (including feet): 5 9/16″
- Width: 14″
- Depth: 11 1/2″
- Construction: Lightweight aluminum chassis with rugged steel cover
- Frequency Range: Amateur 10-meter band
- Types of Emission : AM, FM, CW, SSB, DSB
- Power Output : 200 watts AM with full upward modulation
- Drive Required to Trigger Antenna Relay : 1-watt
- Max Drive (unmodulated carrier and FM): 5 watts (amplitude modulated carrier), 3.5 watts (amplitude modulated peak), 14 watts PEP
- Input Impedance (unbalanced): 50 ohms nominal
- Output Impedance (unbalanced): 50 ohms fixed
- Antenna Switching: Automatic provided by RF sensing circuit
- Power Requirements: 117v AC
- Cable Connector Data : Input & Output requires PL-259
Product Usage Instructions
Section II – Unpacking
Carefully examine the Footwarmer Amplifier upon delivery for any signs of shipping damage. If any damage is observed, immediately file a claim with the carrier responsible for delivery.
Section III – Installation
The location of the mounting is not critical but ensures adequate ventilation for the amplifier. Avoid placing objects on top of the amplifier due to the built-in fan blowing air out of the top.
Once mounted, connect an RG 58/U coaxial cable between the transceiver and the XCVR socket. Attach a 50-ohm antenna to the ANT socket located on the left when viewed from the back.
Check the antenna system for a VSWR of less than 2:1 before using the Footwarmer. Lower VSWR values lead to better communication system performance.
Switches:
- ON-OFF Switch: Controls power to the amplifier.
- AM-FM & SSB Switch: Adjusts delay constant of automatic antenna relay.
FAQ
- Q: What should I do if I notice TV interference after installing the Footwarmer Amplifier?
- A : If you experience TV interference, especially in weak signal areas, consider using a good commercial low pass filter to mitigate the issue.
- Q: Can I use the Footwarmer Amplifier with transceivers lacking external amplifier control circuits?
- A : Yes, the Footwarmer is designed to work without special external connections, making it suitable for operation with low-power transceivers without amplifier control circuits.
INTRODUCTION
The Hy-Gain Footwarmer Amplifier is a precision-built amplifier of advanced design. It utilizes two tubes, and two transistors in a tuned grid-tuned plate circuit for amplification of AM, FM, CW, and SSB signals.
The Footwarmer is designed for 117v AC 60-cycle base installation.
It has a built-in automatic antenna change-over relay, which operates without special external connections, making it perfect for operation with low-power transceivers having no external amplifier control circuits. The Footwarmer has been designed and constructed to suppress radiation that may cause television interference. TVI problem has been given full consideration in the design and the layout of the chassis. There are, however, some types of TVI that cannot be prevented within the amplifier. This is particularly true in weak signal areas. In such cases, a good commercial low-pass filter is recommended.
TECHNICAL SPECIFICATIONS
Mechanical
- Height: (including feet)5 9/16”
- Width: 14″‘
- Depth: 11 1/2′
- Construction: Lightweight aluminum chassis with rugged steel cover
Electrical….
- Frequency Range: Amateur 10-meter band
- Types of Emission: AM, FM, CW, SSB, DSB
- Power Output.. 200 watts AM with full upward modulation
- Drive Required to Trigger Antenna Relay :…. 1 watt
- Max Drive (unmodulated carrier and FM): 5 watts
- (amplitude modulated carrier) …. 3.5 watts
- (amplitude modulated peak): 14 watts PEP
- Input Impedance (unbalanced): …50 ohms nominal
- Output Impedance (unbalanced): ….. 50 ohms fixed
- Antenna Switching: Automatic provided by RF sensing Circuit
- Power Requirements: 117v AC
- Cable Connector Data :.. Input & Output requires PL-259
UNPACKING
Carefully remove the Footwarmer Amplifier from the carton. Examine it closely
for signs of shipping damage. If the inspection shows damage the delivering
carrier must be contacted immediately and a claim filed.
The responsibility for safe delivery rests with the carrier.
The responsibility of obtaining reimbursement rests with you. Prompt action will speed adjustment. Our warranty does not cover malfunction or damage which is a result of improper handling by a carrier.
WARRANTY REGISTRATION
Fill out the enclosed Warranty Card and mail it immediately.
LOCATION
The location of the mounting is not critical, but consideration must be given to provide adequate ventilation. The amplifier has a built-in fan that blows air out of the top. Therefore, care should be taken not to place papers, books, or other objects on top of the amplifier. When the amplifier has been suitably mounted in a convenient position, connect a length of RG 58/U coaxial cable between the transceiver and the XCVR socket. Connect a 50-ohm antenna to the ANT socket (on the left, viewed from the back).
NOTE
The antenna system should be checked for VSWR of less than 2:1 before the
Footwarmer is used. For the best performance of your communication system, the
VSWR should be as low as possible.
CONTROLS AND FUNCTIONS
- ON-OFF Switch: Controls power to the amplifier
- AM-FM & SSB Switch: Adjusts delay constant of automatic antenna relay
- XMT-Standby Switch: Controls the automatic antenna circuit
- Output Meter: … Visual indication of relative RF power output
- Tune-Operate Switch (Rear Panel) ………… Provides for low power tune-up during initial tuning
- Drive Control (Rear Panel): Controls power output for optimum operation
- The side control in the cover is used for tuning the amplifier. The amplifier is returned at 27.575 MHz and the tune control will allow tuning the amplifier to some other frequency.
The side control in the cover is used for tuning the amplifier. The amplifier is returned at 27.575 MHz and the tune control wi II allows tuning the amplifier to some other frequency.
NOTE
THE LOAD CONTROL IS NOT ACCESSIBLE FROM THE OUTSIDE. IT IS PRESET TO PROVIDE A
CORRECT MATCH TO THE 50-OHM ANTENNA SYSTEM. THIS CONTROL SHOULD NOT BE
ADJUSTED. IT IS FACTORY PRESET.
TUNING FOR AM USE: (Requires Wattmeter)
CAUTION
THIS SECTION SHOULD BE READ THOROUGHLY BEFORE OPERATING THE AMPLIFIER.
Place the function switch in the AM-FM position. Push the ON-OFF switch to ON. The red pilot light will come on. After allowing approximately 60 seconds for warm- up, push the XMT Standby switch to XMT. This will ener- gize the automatic antenna relay control circuitry. Set the Slide switch on the rear panel to the Tune position. Adjust the drive control for a midway position. Apply 3.5 watts of drive power by keying the exciter (transceiver) microphone and quickly adjust the tune control for maximum reading on the output meter. Remove the drive power after adjustment.
NOTE
Do not apply drive power for more than five seconds without- out adjusting the
tune control or damage to the tubes can result.
Reapply drive power and adjust the drive control (on the rear panel) so that
the amplifier produces approximately 100 watts output.
The input tuning coil is preset for the 26-35 MHz range. If operated outside
this range it should be reset. To reset the input tuning coil (accessible from
the bottom), first place a VSWR bridge between the linear and the exciter.
Apply drive power and reset the coil slug with a hex-shaped non-metallic
alignment tool for the lowest SWR and maximum output in the “tune” position of
the switch.
Set the Tune-Operate slide switch to the Operate position, reapply drive power and adjust the drive control for 150 watts output on the wattmeter. A readjustment of the input tuning coil may be necessary to produce minimum input VSWR.
NOTE
Always use a good peak reading watt meter such as the Hy-Gain 421A when trying to read Modulation peaks.
Readjust the tune control for maximum output and reset the drive control for 150 watts carrier output.
The amplifier is now adjusted to provide 150 watts carrier and 300 watts with full upward modulation. If the average output power decreases with modulation then either the transmitter (exciter) is incapable of upward modulation or the Amplifier has not been tuned up correctly and the above procedure should be re-checked. If this does not correct the situation, the drive control (on the rear panel) should be adjusted for a slightly lower power level necessary to produce upward modulation. It is far better to have reduced carrier power with upward modulation than a carrier power of a higher level with downward modulation. This will increase your communication range and provide a clearer signal with much less distortion.
The automatic antenna change-over operation in the amplifier is provided by a special transistorized input sensing circuit. Should you desire to hold the amplifier in a ready position, but not use it until needed, simply place the XMT-Standby switch in the Standby position. The sensing circuit will be disabled and the antenna connected to the exciter (transceiver) at all times.
TUNING FOR AM WITHOUT WATTMETER
(26 – 35 MHz)
After proper installation and attachment of a nominal 50-ohm antenna, place the function switch in the AM-FM position and push the ON-OFF switch to ON. The red pilot light will come on. After allowing approximately 60 seconds for warm-up, push the XMT Standby to switch to XMT. This will energize the automatic antenna relay control circuitry. Set the Slide switch on the rear panel to the Tune position.
Adjust the drive control for the midway position. Apply 3.5 watts of drive power by keying the exciter (transceiver) microphone and quickly adjust the tune control for maximum reading on the output meter. Remove the drive power after adjustments.
NOTE
Do not apply drive power for more nan five seconds without- out adjusting the tune control or damage to the tubes can result. Reapply drive power and adjust the drive control for a meter reading of “‘6”. Remove drive power. Set the Tune-Operate switch to the Operate position, re-apply drive power and adjust the drive control for a meter reading of “7”. Readjust the Tune Control for maximum reading on the meter. Reset the drive control for a meter reading of “7”, if necessary.
The amplifier is now adjusted to provide approximately 150 watts of carrier output with full upward modulation to 300 watts. If the meter reading decreases with modulation, either the exciter is incapable of upward modulation or the amplifier has not been tuned correctly and the procedure should be rechecked. If this does not correct the situation the drive control (on the rear panel) should be adjusted for a slightly lower power level necessary to produce upward modulation.
NOTE
Always use a good peak reading watt meter such as the Hy-Gain 421A when trying
to read modulation peaks.
For best AM operation the linear must be tuned according to the above procedures. Many misconceptions regarding linear operation exist among linear users. Reviewing a few points regarding proper linear operation will help to provide better tune-up and communications for the user.
- The linear amplifies the Radio Frequency (RF) signal.
- If the output signal reproduced is identical to the input except stronger, the amplifier is said to be linear. If not, the amplifier is non-linear.
- The non-linear operation produces spurious outputs and distortion of the signal.
- All spurious signals use up power.
- All power used to produce distortion and spurious signals is power not being used for communication.
- The Amplifier provides a 300-watt RF envelope maximum power output.
- Any attempt to operate AM. at the 300-watt carrier level will produce downward modulation with distortion, and spurious signals.
- Distortion and spurious signals (lost power) will occur in all linear amps if operation at maximum carrier power is attempted.
- All linear amplifiers should be operated at about one-half the maximum carrier output to allow for modulation expansion of the carrier.
- Operation without leaving room for modulation expansion will not provide good communication. The carrier contributes nothing toward intelligibility, only good modu- lation can carry intelligence. Running higher carrier power and lower modulation is a detriment rather than an asset.
RETURNING EQUIPMENT FOR SERVICE
DO NOT ship equipment to the Manufacturer without prior authorization. We prefer to send special shipping labels which will avoid the delay of unexpected shipment.
If time is extremely important, wire or call for approval and we will rush labels to you. When a shipment is ex- expected, even the time of sending the labels is less than that lost when an unexpected shipment is received. The shipment must be well-packed and fully insured. Damage claims must be settled between you and the carrier and will greatly delay any returns. Proper packing normally avoids this trouble.
ALL SHIPMENTS MUST BE SENT TO US PREPAID.
We do not accept collected shipments. All returns should be made in our standard cartons only – so save your carton when unpacking the unit. When a shipment is returned it will be handled in one of three ways…
- Where all service is in warranty the shipment will be returned prepaid by a carrier of our choice.
- If there are any charges not covered by warranty we will hold the shipment and advise you of costs, which you can then send.
- Or, upon your written authorization, we will ship COD for any charges not covered by warranty, then the carrier will collect these charges and the transportation costs on arrival. Unclaimed or refused COD shipments will not be
reshipped until payment of service and transportation charges is received. Shipment will then be made collected for reshipment transportation charges. Unclaimed equipment automatically becomes the property of the Manufacturer 60 days after the date of the refusal or return and will be disposed of for payment of the charge due. NOTE We WILL NOT ship by means of a carrier that will not fully insure the shipment. Some carriers have a $200.00 limit.
The exception to this is when there is no other means (APO-FPO-etc.) of shipment than parcel post, and then we will ship by this means with your written agreement that you assume any loss over that which the carrier will insure. COD shipments cannot be made to APO-FPO ad- dresses.
REPLACEMENT PARTS ORDERING
All replacement parts orders must be prepaid or COD only. Replacement part price quotes will be furnished on request for those who desire prepaid shipments or cannot accept COD shipments.
SHIPPING ADDRESS
All requests, inquiries, warranty claims or equipment returns should be made
to: Hy-Gain Electronics Corporation 8601 N.E. Highway 6 Lincoln, Nebraska
68507
Attn: Customer Service Manager
WARRANTY
Hy-Gain Electronics Corporation warrants each new product manufactured to be free from defects in material and workmanship and agrees to remedy any such defect or to furnish a new part, in exchange for any part of any unit which under normal installation, use, and service discloses such defect within ninety days from the date of purchase original owner. The unit serial number must be registered by the original owner at the time of purchase to validate the warranty.
This warranty does not extend to any of our products which have been subjected
to mis-use, neglect, accident, in- correct wiring not our own, improper
installation or to usein violation of instructions furnished by us. Nor does
it extend to units that have been repaired or altered outside of our factory
nor to accessories used therewith not of our own manufacture, nor to any cases
where the serial number has been removed, defaced, or changed.
Hy-Gain Electronics Corporation reserves the right to make any changes deemed
necessary or desirable without advance notice or incurring any obligation to
make like changes in units previously manufactured or sold. This warranty does
not cover transportation or installation costs that may be incurred. Hy-Gain
Electronics Corporation’s sole liability is the remedy of any defect for
ninety days. Hy-Gain Electronics Corporation is not responsible for personal
injury or property damage resulting from improper or careless installation not
intended by the manufacturer.
No person is authorized to assume for us any other liability in connection
with the sale of our products. All warranties are void and terminated one year
after the last unit of its type and design has been manufactured by US.
PARTS LIST
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