<PAGE>
                                                                     Exhibit 4.1


                          REGISTRATION RIGHTS AGREEMENT

         THIS REGISTRATION RIGHTS AGREEMENT (this "AGREEMENT"), dated as of
December 17, 2001, is made by and among ALLEN TELECOM INC., a Delaware
corporation ("BUYER"), BARTLEY R.F. SYSTEMS TRUST, a Massachusetts business
trust (the "PARENT") and BARTLEY R.F. SYSTEMS, INC., a Massachusetts corporation
and a wholly-owned subsidiary of the Parent ("RF SYSTEMS").


                              W I T N E S S E T H:

A.       Pursuant to an Asset Purchase Agreement (the "ASSET PURCHASE
AGREEMENT") dated as of November 19, 2001, by and among Buyer, Parent, RF
Systems, Wenzel/Erlinger Associates, Inc., a California corporation and a
wholly-owned subsidiary of RF Systems ("WENZEL/ERLINGER" and collectively with
RF Systems, the "SELLER") and Richard J. Bartley, Jr., Stephanie J. Bartley, and
Lucy M. Bartley (the "CONTROLLING SHAREHOLDERS"), Buyer has acquired
substantially all of the assets of Seller in exchange for payment of the
Purchase Price as provided therein.

B.       The Purchase Price to be paid to Seller includes the Shares which as of
the date hereof have not been registered under the Securities Act.

C.       In order to induce Parent, Seller and the Controlling Shareholders to
enter into the Asset Purchase Agreement, Buyer has agreed to provide certain
registration rights with respect to the Shares as set forth in this Agreement.

         NOW, THEREFORE, in consideration of the premises and the mutual
covenants contained in this Agreement and other good and valuable consideration
had and received, the parties, on the basis of, and in reliance upon, the
representations, warranties, covenants, obligations and agreements set forth in
this Agreement, and upon the terms and subject to the conditions contained in
this Agreement, hereby agree as follows:

         1.1      DEFINITIONS. All capitalized terms used, but not otherwise
defined, herein have the meanings assigned to them in the Asset Purchase
Agreement. In addition, as used in this Agreement, the following terms have the
following meanings:

                  (a)      "BUSINESS DAY" means a day Monday through Friday on
which banks are generally open for business in New York, New York.

                  (b)      "HOLDERS" means Seller or Parent or any person to
whom the rights under this Agreement have been transferred in accordance with
Section 1.8 hereof.

                  (c)      The terms "REGISTER," "REGISTERED" and "REGISTRATION"
refer to the registration effected by preparing and filing a registration
statement in compliance with the Securities Act, and the declaration or ordering
of the effectiveness of such registration statement.


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                  (d)      "REGISTRABLE SECURITIES" means the Closing Shares and
the Escrow Shares, together with any securities that may be issued or
distributed in respect of such shares by way of stock dividend, stock split or
other distribution, or by way of merger, consolidation, exchange offer,
reorganization or reclassification or similar transaction; provided, however,
that securities will only be treated as Registrable Securities if and only for
so long as they (A) have not been disposed of pursuant to a registration
statement declared effective by the Securities and Exchange Commission ("SEC"),
(B) have not been sold in a transaction exempt from the registration and
prospectus delivery requirements of the Securities Act so that all transfer
restrictions and restrictive legends with respect thereto are removed upon the
consummation of such sale, (C) are held by a Holder or a permitted transferee
pursuant to Section 1.8 hereof, or (D) have not been sold or are not available
for sale in transactions pursuant to Rule 144(k) promulgated under the
Securities Act.

                  (e)      "REGISTRATION EXPENSES" means all reasonable expenses
incurred by the Buyer in complying with this Agreement, including all
registration, qualification and filing fees, reasonable printing and duplicating
expenses, fees and expenses of counsel and accountants for the Buyer, listing
fees and expenses, blue sky fees and expenses and the reasonable expense of any
special audits incident to or required by any such registration (but excluding
Selling Expenses).

                  (f)      "REGISTRATION PERIOD" has the meaning ascribed to
such term in Section 1.4.

                  (g)      "REGISTRATION STATEMENT" has the meaning ascribed to
such term in Section 1.2.

                  (h)      "SELLING EXPENSES" means all underwriting discounts
and selling commissions applicable to the sale of Registrable Securities and all
fees and expenses of legal counsel for any Holder.

         1.2      SHELF REGISTRATION. No later than five Business Days after the
Closing Date (the "FILING DATE"), the Buyer shall file a "shelf" registration
statement on the appropriate form (the "REGISTRATION STATEMENT") with the SEC
and use its reasonable best efforts to effect the registration, qualification or
compliance (including the execution of any required undertaking to file
post-effective amendments, appropriate qualifications or exemptions under
applicable blue sky or other state securities laws and appropriate compliance
with applicable securities laws, requirements or regulations) of the Registrable
Securities for resale by the Holders as soon as is reasonably practical
thereafter.

         1.3      REGISTRATION EXPENSES. Buyer shall pay all Registration
Expenses incurred in connection with any registration, qualification, exemption
or compliance pursuant to Section 1.2.

         1.4      OBLIGATIONS OF THE BUYER. In the case of the registration,
qualification, exemption or compliance effected by the Buyer pursuant to this
Agreement, the Buyer shall, upon reasonable request, inform each Holder as to
the status of such registration, qualification, exemption and compliance. At its
expense the Buyer shall:


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                  (a)      use its commercially reasonable efforts to keep such
registration, and any qualification, exemption or compliance under state
securities laws that the Buyer determines to obtain, continuously effective
until the Holders have completed the distribution described in the registration
statement relating thereto. The period of time during which the Buyer is
required hereunder to keep the Registration Statement effective is referred to
herein as the "REGISTRATION PERIOD." Notwithstanding the foregoing, at the
Buyer's election, the Buyer may cease to keep such registration, qualification,
exemption or compliance effective with respect to any Registrable Securities,
and the registration rights of a Holder will expire, at such time as they are no
longer, by reason of Rule 144 promulgated under the Securities Act (or other
exemption from registration acceptable to the Buyer) required to register for
the sale thereof;

                  (b)      promptly as reasonably practicable advise the
Holders:

                           (i)      when the Registration Statement or any
amendment thereto has been filed with the SEC and when the Registration
Statement or any post-effective amendment thereto has become effective;

                           (ii)     of any request by the SEC for amendments or
supplements to the Registration Statement or the prospectus included therein or
for additional information;

                           (iii)    of the issuance by the SEC of any stop order
suspending the effectiveness of the Registration Statement or the initiation of
any proceedings for such purpose;

                           (iv)     of the receipt by the Buyer of any
notification with respect to the suspension of the qualification of the
Registrable Securities included therein for sale in any jurisdiction or the
initiation or threatening of any proceeding for such purpose; and

                           (v)      of the happening of any event that requires
the making of any changes in the Registration Statement or the prospectus so
that, as of such date, the statements therein are not misleading and do not omit
to state a material fact required to be stated therein or necessary to make the
statements therein (in the case of the prospectus, in the light of the
circumstances under which they were made) not misleading;

                  (c)      every reasonable effort to obtain the withdrawal of
any order suspending the effectiveness of any Registration Statement at the
earliest possible time;

                  (d)      furnish to each Holder upon request, without charge,
at least one copy of such Registration Statement in the form it becomes
effective and any post-effective amendment thereto, including financial
statements and schedules, and, if the Holder so requests in writing, all
exhibits (including those incorporated by reference) in the form filed with the
SEC;

                  (e)      during the Registration Period, deliver to each
Holder, without charge, as many copies of the prospectus included in such
Registration Statement and any amendment or supplement thereto as such Holder
may reasonably request; and the Buyer consents to the use, consistent with the
provisions hereof, of the prospectus or any amendment or supplement thereto by
each of the selling Holders of Registrable Securities in connection with the
offering and sale of the Registrable Securities covered by the prospectus or any
amendment or supplement thereto;


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                  (f)      prior to any public offering of Registrable
Securities pursuant to any Registration Statement, register or qualify or obtain
an exemption for offer and sale under the securities or blue sky laws of such
jurisdictions as any such Holders reasonably request in writing, provided,
however, that the Buyer shall not for any such purpose be required to qualify
generally to transact business as a foreign corporation in any jurisdiction
where it is not so qualified or to consent to general services of process in any
such jurisdiction, and do any and all other acts or things reasonably necessary
or advisable to enable the offer and sale in such jurisdictions of the
Registrable Securities covered by such Registration Statement;

                  (g)      cooperate with the Holders to facilitate the timely
preparation and delivery of certificates representing Registrable Securities to
be sold pursuant to any Registration Statement free of any restrictive legends
in such denominations and registered in such names as Holders may request at
least three (3) business days prior to sales of Registrable Securities pursuant
to such Registration Statement;

                  (h)      upon the occurrence of any event contemplated by
Section 1.4(b)(v) above, the Buyer shall promptly prepare a post-effective
amendment to the Registration Statement or a supplement to the related
prospectus, or file any other required document so that, as thereafter delivered
to purchasers of the Registrable Securities included therein, the prospectus
will not include any untrue statement of a material fact or omit to state any
material fact necessary to make the statements therein, in light of the
circumstances under which they were made, not misleading.

                  (i)      use its reasonable best efforts to comply with all
applicable rules and regulations of the SEC and make generally available to its
security holders, as soon as reasonably practicable (but not more than fifteen
months) after the effective date of any Registration Statement, an earnings
statement satisfying the provisions of Section 11(a) of the Securities Act and
the rules and regulations thereunder;

                  (j)      provide and cause to be maintained a transfer agent
and registrar for all Registrable Securities covered by a Registration Statement
from and after a date not later than the effective date of such Registration
Statement; and

                  (k)      cause all Registrable Securities covered by a
Registration Statement to be listed on the primary securities exchange or
inter-dealer quotation system on which such securities of that type are then
listed or quoted.

         1.5      INDEMNIFICATION.

                  (a)      To the extent permitted by law, the Buyer shall
indemnify each Holder and each person controlling such Holder within the meaning
of Section 15 of the Securities Act, with respect to which any registration,
qualification or compliance has been effected pursuant to this Agreement,
against all claims, losses, damages, liabilities and expenses (or action in
respect thereof), including any of the foregoing incurred in settlement of any
litigation, commenced or threatened (subject to Section 1.5(c) below), arising
out of or based on any untrue statement (or alleged untrue statement) of a
material fact contained in any registration statement or prospectus, or any
amendment or supplement thereof, incident to any such registration,
qualification or


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compliance, or based on any omission (or alleged omission) to state therein a
material fact required to be stated therein or necessary to make the statements
therein not misleading, in light of the circumstances in which they were made,
and shall reimburse each Holder and each person controlling such Holder, for
reasonable legal and other expenses reasonably incurred in connection with
investigating or defending any such claim, loss, damage, liability or action as
incurred; provided, however, that the Buyer will not be liable in any such case
to the extent that any untrue statement or omission or allegation thereof is
made in reliance upon and in conformity with written information furnished to
the Buyer by or on behalf of such Holder and stated to be specifically for use
in preparation of such registration statement, prospectus or offering circular;
and provided further, that the Buyer will not be liable in any such case where
the claim, loss, damage or liability arises out of or is related to the failure
of the Holder to comply with the covenants and agreements contained in the Asset
Purchase Agreement respecting sales of Registrable Securities, and except that
the foregoing indemnity agreement is subject to the condition that, insofar as
it relates to any such untrue statement or alleged untrue statement or omission
or alleged omission made in the preliminary prospectus but eliminated or
remedied in the amended prospectus on file with the SEC at the time the
registration statement becomes effective or in the amended prospectus filed with
the SEC pursuant to Rule 424(b) or in the prospectus subject to completion and
term sheet under Rule 434 of the Securities Act, which together meet the
requirements of Section 10(a) of the Securities Act (the "FINAL PROSPECTUS"),
such indemnity agreement will not inure to the benefit of any such Holder or any
such controlling person, if a copy of the Final Prospectus furnished by the
Buyer to the Holder for delivery was not furnished to the person or entity
asserting the loss, liability, claim or damage at or prior to the time such
furnishing is required by the Securities Act and the Final Prospectus would have
cured the defect giving rise to such loss, liability, claim or damage.

                  (b)      Each Holder shall severally, if Registrable
Securities held by such Holder are included in the securities as to which such
registration, qualification or compliance is being effected, indemnify the
Buyer, each of its directors and officers, each underwriter of the Registrable
Securities and each person who controls the Buyer within the meaning of Section
15 of the Securities Act, against all claims, losses, damages and liabilities
(or actions in respect thereof), including any of the foregoing incurred in
settlement of any litigation, commenced or threatened (subject to Section 1.5(c)
below), arising out of or based on any untrue statement ( or alleged untrue
statement) of a material fact contained in any registration statement or
prospectus, or any amendment or supplement thereof, incident to any such
registration, qualification or compliance, or based on any omission (or alleged
omission) to state therein a material fact required to be stated therein or
necessary to make the statements therein not misleading, in light of the
circumstances in which they were made, and shall reimburse the Buyer, such
directors and officers, each underwriter of the Registrable Securities and each
person controlling the Buyer for reasonable legal and any other expense
reasonably incurred in connection with investigating or defending any such
claim, loss, damage, liability or action as incurred, in each case to the
extent, but only to the extent, that such untrue statement or omission or
allegation thereof is made in reliance upon and in conformity with written
information furnished to the Buyer by or on behalf of the Holder and stated to
be specifically for use in preparation of such registration statement,
prospectus or offering circular; provided, however, that the indemnity will not
apply to the extent that such claim, loss, damage or liability results from the
fact that a current copy of the prospectus was not made available to the Holder
and such current copy of the prospectus would have cured the defect giving rise
to such loss, claim, damage or liability. Notwithstanding the


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foregoing, in no event will a Holder be liable for any such claims, losses,
damages or liabilities in excess of the proceeds received by such Holder in the
offering, except in the event of fraud by such Holder.

                  (c)      Each party entitled to indemnification under this
Section 1.5 (the "INDEMNIFIED PARTY") shall give notice to the party required to
provide indemnification (the "INDEMNIFYING PARTY") promptly but in no event
later than 10 days after such Indemnified Party has actual knowledge of any
claim as to which indemnity may be sought, and shall permit the Indemnifying
Party to assume the defense of any such claim or any litigation resulting
therefrom; provided, however, that counsel for the Indemnifying Party, who
conducts the defense of such claim or litigation, must be reasonably acceptable
to the Indemnified Party, and the Indemnified Party may participate in such
defense at such Indemnified Party's expense; and provided further, that the
failure of any Indemnified Party to give notice as provided herein will not
relieve the Indemnifying Party of its obligations under this Agreement, unless
such failure is materially prejudicial to the Indemnifying Party in defending
such claim or litigation. An Indemnifying Party will not be liable for any
settlement of an action or claim effected without its written consent.

                  (d)      If the indemnification provided for in this Section
1.5 is held by a court of competent jurisdiction to be unavailable to an
Indemnified Party with respect to any loss, liability, claim, damage or expense
referred to therein, then the Indemnifying Party, in lieu of indemnifying such
Indemnified Party thereunder, shall contribute to the amount paid or payable by
such Indemnified Party as a result of such loss, liability, claim, damage or
expense in such proportion as is appropriate to reflect the relative fault of
the Indemnifying Party on the one hand and of the Indemnified Party on the other
in connection with the statements or omissions that resulted in such loss,
liability, claim, damage or expense as well as any other relevant equitable
considerations. The relative fault of the Indemnifying Party and of the
Indemnified Party will be determined by reference to, among other things,
whether the untrue or alleged untrue statement of a material fact or the
omission to state a material fact relates to information supplied by the
Indemnifying Party or by the Indemnified Party and the parties' relative intent,
knowledge, access to information and opportunity to correct or prevent such
statement or omission.

         1.6      OBLIGATIONS OF THE HOLDERS.

                  (a)      Each Holder agrees that, upon receipt of any notice
from the Buyer of the happening of any event requiring the preparation of a
supplement or amendment to a prospectus relating to Registrable Securities so
that, as thereafter delivered to the Holders, such prospectus will not contain
an untrue statement of a material fact or omit to state any material fact
required to be stated therein or necessary to make the statements therein not
misleading, each Holder will forthwith discontinue disposition of Registrable
Securities pursuant to the registration statement contemplated by Section 1.2
until its receipt of copies of the supplemented or amended prospectus from the
Buyer and, if so directed by the Buyer, each Holder shall deliver to the Buyer
all copies, other than permanent file copies then in such Holder's possession,
of the prospectus covering such Registrable Securities current at the time of
receipt of such notice.

                  (b)      Each Holder shall suspend, upon request of the Buyer,
any disposition of Registrable Securities pursuant to the Registration Statement
and prospectus contemplated by


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Section 1.2 during (i) any period not to exceed two 90-day periods within any
one 12-month period the Buyer requires in connection with a primary underwritten
offering of equity securities and (ii) any period, not to exceed one 45-day
period per circumstance or development, when the Buyer determines in good faith
that offers and sales pursuant thereto should not be made by reason of the
presence of material undisclosed circumstances or developments with respect to
which the disclosure that would be required in such a prospectus is premature,
would have an adverse effect on the Buyer or is otherwise inadvisable.

                  (c)      As a condition to the inclusion of its Registrable
Securities, each Holder shall furnish to the Buyer such information regarding
such Holder and the distribution proposed by such Holder as the Buyer may
request in writing or as is required in connection with any registration,
qualification or compliance referred to in this Agreement.

                  (d)      Each Holder hereby covenants with the Buyer (i) not
to make any sale of the Registrable Securities without effectively causing the
prospectus delivery requirements under the Securities Act to be satisfied, and
(ii) if such Registrable Securities are to be sold by any method or in any
transaction other than on a national securities exchange, Nasdaq National
Market, Nasdaq SmallCap Market or in the over-the-counter market, in privately
negotiated transactions, or in a combination of such methods, to notify the
Buyer at least five (5) business days prior to the date on which the Holder
first offers to sell any such Registrable Securities.

                  (e)      Each Holder acknowledges and agrees that the
Registrable Securities sold pursuant to the Registration Statement described in
this Section are not transferable on the books of the Buyer unless the stock
certificate submitted to the transfer agent evidencing such Registrable
Securities is accompanied by a certificate reasonably satisfactory to the Buyer
to the effect that (i) the Registrable Securities have been sold in accordance
with such Registration Statement and (ii) the requirement of delivering a
current prospectus has been satisfied.

                  (f)      Each Holder agrees not to take any action with
respect to any distribution deemed to be made pursuant to such registration
statement that would constitute a violation of Regulation M under the Securities
Exchange Act of 1934, as amended (the "EXCHANGE ACT"), or any other applicable
rule, regulation or law.

                  (g)      At the end of the period during which the Buyer is
obligated to keep the Registration Statement current and effective as described
above, the Holders of Registrable Securities included in the Registration
Statement shall discontinue sales of shares pursuant to such Registration
Statement upon receipt of notice from the Buyer of its intention to remove from
registration the shares covered by such Registration Statement that remain
unsold, and such Holders shall notify the Buyer of the number of shares
registered that remain unsold immediately upon receipt of such notice from the
Buyer.

         1.7      RULE 144 REPORTING. With a view to making available to the
Holders the benefits of certain rules and regulations of the SEC that at any
time permit the sale of the Registrable Securities to the public without
registration, the Buyer shall use its reasonable best efforts to:

                  (a)      make and keep public information available as those
terms are understood and defined in Rule 144 under the Securities Act, at all
times;


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                  (b)      file with the SEC in a timely manner all reports and
other documents required of the Buyer under the Exchange Act; and

                  (c)      so long as a Holder owns any unregistered Registrable
Securities, furnish to such Holder, upon any reasonable request, a written
statement by the Buyer as to its compliance with Rule 144 under the Securities
Act, and of the Exchange Act, a copy of the most recent annual or quarterly
report of the Buyer, and such other reports and documents of the Buyer as such
Holder may reasonably request in availing itself of any rule or regulation of
the SEC allowing a Holder to sell any such securities without registration.

         1.8      ASSIGNABILITY. The rights to cause the Buyer to register
Registrable Securities granted to the Holders by the Buyer under Section 1.1 may
be assigned in full by a Holder in connection with a transfer by such Holder of
all of its Registrable Securities; provided, however, that (i) such transfer
must otherwise be effected in accordance with applicable securities laws; (ii)
such Holder gives prior written notice to the Buyer; and (iii) such transferee
agrees to comply with the terms and provisions of this Agreement, and such
transfer is otherwise in compliance with the Asset Purchase Agreement. Except as
specifically permitted by this Section 1.8, the rights of a Holder with respect
to Registrable Securities as set out herein will not be transferable to any
other Person, and any attempted transfer will cause all rights of such Holder
therein to be forfeited. Subject to the foregoing, this Agreement shall be
binding upon and shall inure to the benefit of the parties hereto and their
respective successors and permitted assigns.

         1.9      AMENDMENTS AND WAIVERS. With the written consent of the Buyer
and the Holders holding at least a majority of the Registrable Securities that
are then outstanding, any provision of this Agreement may be waived (either
generally or in a particular instance, either retroactively or prospectively and
either for a specified period of time or indefinitely) or amended. Upon the
effectuation of each such waiver or amendment, the Buyer shall promptly give
written notice thereof to the Holders, if any, who have not previously received
notice thereof or consented thereto in writing.

         1.10     NOTICES. All notices and other communications required or
permitted hereunder shall be in writing and shall be deemed to have been duly
given when delivered in person or five business days after being sent by
registered or certified mail, return receipt requested, postage prepaid, to the
appropriate party at the address specified below:

                  If to Parent or RF Systems:

                                    Richard J. Bartley, Jr.
                                    93 Hilldale Avenue
                                    South Hampton, New Hampshire 03827

                  with a copy to:

                                    Nixon Peabody LLP
                                    101 Federal Street
                                    Boston, Massachusetts  02110-1823
                                    Attention:  Charles F. Claeys, P.C.


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                  If to Buyer:
                                    ALLEN TELECOM INC.
                                    25101 Chagrin Blvd. #350
                                    Beachwood, Ohio  44122
                                    Attention:  General Counsel

                  with a copy to:
                                    Jones, Day, Reavis & Pogue
                                    North Point
                                    901 Lakeside Avenue
                                    Cleveland, Ohio  44114
                                    Attention:  Charles W. Hardin, Jr.


Any party hereto may change its address for the purposes of this SECTION 1.10 by
giving notice as provided herein.

         1.11     COUNTERPARTS. This Agreement may be executed in any number of
counterparts, each of which will be deemed to be an original, and all of which
together will constitute one and the same instrument.

         1.12     HEADINGS. The headings in this Agreement are solely for
convenience of reference and are not to be given any effect in the construction
or interpretation of this Agreement.


                         [SIGNATURES ON FOLLOWING PAGE]




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                  IN WITNESS WHEREOF, the parties have caused their duly
authorized representatives to execute this Agreement as of the date first above
written.


                                       ALLEN TELECOM INC.


                                       By: /s/ Laura C. Meagher
                                          ------------------------------------
                                          Name:  Laura C. Meagher
                                          Title: Secretary


                                       BARTLEY R.F. SYSTEMS TRUST


                                       By: /s/ Richard J. Bartley, Jr.
                                          ------------------------------------
                                          Name:  Richard J. Bartley, Jr.
                                          Title: President


                                       BARTLEY R.F. SYSTEMS, INC.


                                       By: /s/ Richard J. Bartley, Jr.
                                          ------------------------------------
                                          Name:  Richard J. Bartley, Jr.
                                          Title: President




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